WO2002081441A1 - Process for the preparation of substituted pyrrolidine neuraminidase inhibitors - Google Patents

Process for the preparation of substituted pyrrolidine neuraminidase inhibitors Download PDF

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Publication number
WO2002081441A1
WO2002081441A1 PCT/US2002/008074 US0208074W WO02081441A1 WO 2002081441 A1 WO2002081441 A1 WO 2002081441A1 US 0208074 W US0208074 W US 0208074W WO 02081441 A1 WO02081441 A1 WO 02081441A1
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compound
structural formula
alkyl
tert
methoxy
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PCT/US2002/008074
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French (fr)
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Steven J. Wittenberger
Lakshmi Bhagavatula
David A. Degoey
John Demattei
David R. Hill
Maureen A. Mclaughlin
Ashok K. Gupta
Sukumar Manna
Paul J. Nichols
Premchandran H. Ramiya
Zhenping Tian
Michael W. Rasmussen
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Abbott Laboratories
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Publication of WO2002081441A1 publication Critical patent/WO2002081441A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D207/00—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom
    • C07D207/02—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D207/18—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having one double bond between ring members or between a ring member and a non-ring member
    • C07D207/22—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having one double bond between ring members or between a ring member and a non-ring member with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D207/24—Oxygen or sulfur atoms
    • C07D207/26—2-Pyrrolidones
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
    • A61P31/12—Antivirals
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D207/00—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom
    • C07D207/02—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D207/04—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members
    • C07D207/10—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D207/12—Oxygen or sulfur atoms
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D207/00—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom
    • C07D207/02—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D207/04—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members
    • C07D207/10—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D207/16—Carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals

Definitions

  • This invention is directed to a process for making substituted pyrrolidine neuraminidase inhibitors and to intermediates which are useful in the process.
  • Drugs such as zanamivr (Relenza ) are known in the art as agents which inhibit neuraminidases and are therefore potentially useful for the treatment and prophylaxis of influenza (N EnglJ Med 2000; 343(18): 1282-9).
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyalkyl, or aryl-(C 2 -C 4 -alkyl); R is
  • This invention is directed to a synthesis of inhibitors of neuraminidases in which column chromatographic purification is omitted; in which steps are conducted sequentially, in situ, and continuously; and in which critical reaction parameters such as agents employed and ratios of the same, solvents, temperatures, and times are optimized to provide a more cost-efficient synthesis than that disclosed in the 787 application.
  • steps conducted sequentially means conduction of a plurality of steps without work-up between the steps.
  • steps conducted in situ means conduction of a plurality of steps with a workup between the steps and during which the product remains in solution. Steps conducted in situ can be accompanied by solvent exchange, during which one solvent or solvents is substantially exchanged for another solvent or solvents and during which exchange the product remains in solution.
  • steps conducted continuously means the conduction of a step followed by work-up and solvent removal before beginning a subsequent step.
  • alkoxy means an alkyl radical attached to the parent molecular group through an oxygen atom
  • alkoxycarbonyl means an alkoxy radical attached to the parent molecular group through a carbonyl
  • alkyl means a saturated, monovalent straight or branched hydrocarbon radical having one to six carbon atoms
  • aryl means a six-membered aromatic, carbocyclic ring which is unsubstituted or substituted by independent replacement of a hydrogen atom or atoms thereon by an alkyl, alkoxy, halo, or nitro radical
  • arylalkyl means an alkyl radical derivatized by the replacement of a hydrogen atom thereon by an aryl radical
  • aryl-(C 2 -C 4 -alkyl) means an alkyl radical having two
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl, comprising the steps of: (a) reacting a compound having s
  • step (b) reacting the product of step (a) and a first reducing agent to provide a compound having structural formula (3)
  • step (c) reacting the product of step (b) and a titanium w ⁇ -propoxide-dialkyl tartrate complex
  • step (d) reacting the product of step (c) and tert-butyl hydroperoxide to provide a compound having structural formula (4)
  • step (e) reacting the product of step (d) and a second reducing agent to provide the compound having structural formula (5), a preferred embodiment of which is the compound having the stereochemistry illustrated by a compound having structural formula (5-a)
  • R z OH (5-a) and a more preferred embodiment of which is substantially pure, enantiomerically enriched
  • steps (c) and (d) are conducted sequentially, and steps (d) and (e) are conducted continuously.
  • first acids useful for the practice of step (a) include hydrochloric acid, perchloric acid, phosphoric acid, sulfuric acid, trifluoroacetic acid, and the like.
  • a preferred acid for the practice of step (a) is sulfuric acid.
  • first esterifying agents useful for the practice of step (a) include ⁇ o-butylene, a CpC 4 alcohol such as methanol, ethanol, z ' so-propanol, ter/-butyoxycarbonyl-2-( 1 -acetamido-2-methoxy-2-methyl)pentyl-3-(cis-propeny- 1 - yl)pyrrolidine-5-carboxylic acid tert-butyl ester, and the like.
  • a preferred first esterifying agent for the practice of step (a) is methanol.
  • Examples of trialkylorthoformates useful for the practice of step (a) include trimethylorthoformate, triethylorthoformate, and tri-wo-propylorthoformate.
  • a preferred trialkylorthoformate for the practice of step (a) is trimethylorthoformate .
  • Step (a) is conducted at a temperature between about 25 °C and 100 °C in a C]-C 5 alcohol solvent such as methanol, ethanol, ts ⁇ -propanol, «-butanol, and the like.
  • a C]-C 5 alcohol solvent such as methanol, ethanol, ts ⁇ -propanol, «-butanol, and the like.
  • step (a) is conducted at about 60 °C in essentially methanol.
  • first reducing agents useful for the practice of step (b) include lithium borohydride, lithium borohydride pyrrolidine, lithium triethylborohydride, lithium triethylborohydride, potassium triethylborohydride, potassium tri(sec-butyl)borohydride, potassium triphenylborohydride, aluminum hydride, aluminum hydride triethylamine, di(zs ⁇ -butyl)aluminum hydride, is ⁇ -propoxyaluminum hydride, tert-butoxyaluminum hydride, di(tert-butoxy)aluminum hydride, lithium aluminum hydride, lithium aluminum hydride N-methylpyrrolidine, sodium aluminum hydride, sodium diethylaluminum hydride, bis(2-methoxyethoxy)aluminum hydride, lithium di(wo-butyl)aluminum hydride, and the like.
  • a preferred first reducing agent for the practice of step (b) is di(iso- butyl)aluminum hydride.
  • Step (b) is conducted at a temperature between about -60 °C and about -50 °C in a solvent such as diethyl ether, hexane, heptane, tetrahydrofuran, or a mixture thereof.
  • a solvent such as diethyl ether, hexane, heptane, tetrahydrofuran, or a mixture thereof.
  • step (b) is conducted at about -60 °C in essentially hexane.
  • step (c) is prepared by reacting titanium w ⁇ -propoxide and a dialkyl tartrate.
  • dialkyl tartrate employed for the practice of step (c) is D-dimethyl tartrate, D-diethyl tartrate, or D-diisopropyl tartrate. More preferably the dialkyl tartrate employed for the practice of step (c) is
  • Step (c) is conducted at a temperature between about -10 °C and about -30 °C in a solvent such as dichloromethane, chloroform, carbon tetrachloride, or a mixture thereof. In a preferred embodiment, step (c) is conducted at about -20 °C in essentially dichloromethane.
  • Step (d) is conducted at a temperature of between about -30 °C and about -50 °C in a solvent such as carbon tetrachloride, chloroform, decane, dichloromethane, hexane, heptane, pentane, or a mixture thereof.
  • a solvent such as carbon tetrachloride, chloroform, decane, dichloromethane, hexane, heptane, pentane, or a mixture thereof.
  • step (d) is conducted at about -40 °C in essentially a mixture of decane and dichloromethane.
  • both the titanium ts ⁇ -propoxide dialkyl tartrate complex and the tert-butyl hydroperoxide in steps (c) and (d), respectively are each present in about 0.3 molar equivalents per molar equivalent of the compound having structural formula (3), and the compound having formula (4) has an enantiomeric excess of between about 86% and 89%.
  • both the titanium wo-propoxide dialkyl tartrate complex and the tert-butyl hydroperoxide in steps (c) and (d), respectively are each present in about 1.0 molar equivalent per molar equivalent of the compound having structural formula (3), and the compound having formula (4) has an enantiomeric excess of between about 94% and about 97%.
  • second reducing agents useful for the practice of step (e) include borane dimethylsulfide, borane tetrahydrofuran, borane and boron trifluoride diethyletherate, borane sodium borohydride, lithium borohydride, lithium borohydride py ⁇ olidine, lithium triethylborohydride, lithium triethylborohydride, potassium triethylborohydride, potassium tri(.sec-butyl)borohydride, potassium triphenylborohydride, aluminum hydride, aluminum hydride-triethylamine, di(wo-butyl)aluminum hydride, wo-propoxyaluminum hydride, tert-butoxyaluminum hydride, di(tert-butoxy)aluminum hydride, lithium aluminum hydride, lithium aluminum hydride-N-methylpyrrolidine, sodium alummum hydride, sodium diethylaluminum hydride, bis
  • a prefe ⁇ ed second reducing agent for the practice of step (e) is lithium aluminum hydride.
  • Step (e) is conducted at a temperature between about -30 °C and about -50 °C in a solvent such as diethylether, dioxane, tetrahydrofuran, or a mixture thereof.
  • step (e) is conducted at about -40 °C in essentially tetrahydrofuran.
  • step (f) is conducted, and the product of step (e) is isolated by distillation.
  • a compound having structural formula (5) is useful as an intermediate for making a compound having structural formula (12)
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; and R is alkyl, cycloalkyalkyl, or aryl-(C 2 -C -alkyl).
  • a process for making a compound having structural formula (12) from the compound having structural formula (5) comprising, in toto, the steps of: (g) reacting the compound having structural formula (5)
  • R 2 OH (5) a preferred embodiment of which is a compound having the stereochemistry illustrated by a compound having structural formula (5-a)
  • step (h) reacting the product of step (g), an alkylating agent, and the first base to provide a compound having structural formula (7)
  • step (i) reacting the product of step (h) and a hydroxy protecting group removal agent to provide the compound having structural formula (12), a prefe ⁇ ed embodiment of which is a compound having the stereochemistry illustrated by a compound having structural formula (12-a)
  • steps (g) and (h) are conducted sequentially, and steps (h) and (i) are conducted continuously.
  • first bases useful for the practice of step (g) and step (h) include dibutyltin oxide, lithium diisopropylamide, sodium hydride, potassium hydride, lithium bis(trimethylsilylamide), sodium bis(trimethylsilylamide), potassium bis(trimethylsilylamide), lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, lithium tert-amylate, sodium tert-amylate, potassium tert-amylate, and the like.
  • a preferred first base for the practice of step (g) and step (h) is sodium hydride.
  • Examples of selectively removable hydroxy protecting group precursors for the practice of step (g) include methoxymethyl bromide, methoxymethyl chloride, methylthiomethyl bromide, methylthiomethyl chloride,
  • ra-xylylsilyl bromide tri-p ⁇ ra-xylylsilyl chloride, triphenylsilyl bromide, triphenylsilyl chloride, diphenylmethylsilyl bromide, diphenylmethylsilyl chloride, di-tert-butylmethylsilyl bromide, di-tert-butylmethylsilyl chloride, tris(trimethylsilyl)silyl, tris(trimethylsilyl)silyl, (2-hydroxystyryl)dimethylsilyl bromide,
  • Prefe ⁇ ed selectively removable hydroxy protecting group precursors for the practice of step (g) include benzyl chloride, benzyl bromide, diphenylmethyl chloride, diphenylmethyl bromide, ⁇ r ⁇ -methoxybenzyl chloride, /? ⁇ r ⁇ -methoxybenzyl bromide, 3,4-dimethoxybenzyl chloride, 3,4-dimethoxybenzyl bromide, ⁇ rtAonitrobenzyl chloride, ⁇ rt ⁇ -nitrobenzyl bromide, /j ⁇ r ⁇ -nitrobenzyl chloride, /? ⁇ ra-nitrobenzyl bromide, 2,6-dichlorobenzyl chloride, 2,6-dichlorobenzyl bromide, 2,6-difluorobenzyl chloride, 2,6-difluorobenzyl bromide, 2-trifluoromethylbenzyl chloride, 2-trifluoromethylbenzyl bromide, /r
  • More prefe ⁇ ed selectively removable hydroxy protecting group precursors for the practice of step (g) are benzyl chloride or benzyl bromide.
  • alkylating agents useful for the practice of step (h) are alkyl halides such as methyl chloride, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, z ' s ⁇ -propyl chloride, wo-propyl bromide, ts ⁇ -propyl iodide, and the like; alkyl trifluoromethanesulfonates such as methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, w ⁇ -propyl trifluoromethanesulfonate, and the like; dialkylsulfates such as dimethylsulfate, diethylsulfate, diisopropylsulfate, and the like; cycloalkyalkyl halides such as (chloromethyl)cyclopropane, (bromoethyl
  • a preferred alkylating agent for the practice of step (h) is methyl iodide.
  • Steps (g) and (h) are conducted at a temperature between about -10 °C and about 30 °C in a solvent such as diethyl ether, tetrahydrofuran, dioxane, 1 ,2-dimethoxyethane, NN-dimethylformamide, toluene, dimethylsulfoxide, acetonitrile, or a mixture thereof.
  • steps (g) and (h) are conducted at about 0 °C in tetrahydrofuran.
  • hydroxy protecting group removal agents useful for the practice of step (i) are hydrogen gas and a hydrogenolysis catalyst such as palladium metal, palladium metal on carbon, palladium metal on neutral alumina, palladium metal on acidic alumina, palladium metal on basic alumina, palladium(II) acetate, palladium(II) chloride, palladium(H) hydroxide on carbon, and the like.
  • a preferred hydrogenolysis catalyst for the practice of step (i) is palladium(II) hydroxide on carbon.
  • Step (i) is conducted at a temperature of between about 0 °C and about 30 °C, at a pressure of about 10 pounds per square inch to about 80 pounds per square inch, in a solvent such as acetone, diethyl ether, dioxane, methanol, ethanol, w ⁇ -propanol, tert-butanol, ethyl acetate, iso-propy ⁇ acetate, methylethyl ketone, tetrahydrofuran, or a mixture thereof.
  • a solvent such as acetone, diethyl ether, dioxane, methanol, ethanol, w ⁇ -propanol, tert-butanol, ethyl acetate, iso-propy ⁇ acetate, methylethyl ketone, tetrahydrofuran, or a mixture thereof.
  • step (i) is conducted at about 25 °C, at a pressure of about 40 pounds per square inch, in essentially tetrahydrofuran.
  • step (j) is conducted, and the product of step (i) is isolated by distillation.
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; and R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl, comprising the steps of: (k) reacting a compound having structural formula (8)
  • step (10) (1) reacting the product of step (k), a second esterifying agent and, optionally, an esterification promotion agent to structural formula (10)
  • R is alkyl, C 2 -C 4 -haloalkyl, cycloalkylalkyl, or arylalkyl, a preferred embodiment of which is substantially pure
  • steps (m) and (n) are conducted continuously, and step (o) is omitted.
  • step (k) is conducted at about 60 °C.
  • second esterifying agents useful for the practice of step (1) include z ' s ⁇ -butylene, a -C alcohol such as methanol, ethanol, and ⁇ -propanol, tert-butyoxycarbonyl-2-(l-acetamido-2-methoxy-2-methyl)pentyl-3-(cis-propeny-l- yl)pyrrolidine-5-carboxylic acid tert-butyl ester, and the like, and, optionally an acid such as hydrochloric acid or sulfuric acid.
  • a -C alcohol such as methanol, ethanol, and ⁇ -propanol
  • tert-butyoxycarbonyl-2-(l-acetamido-2-methoxy-2-methyl)pentyl-3-(cis-propeny-l- yl)pyrrolidine-5-carboxylic acid tert-butyl ester and the like, and, optionally an acid such as hydrochloric acid or sulfur
  • the alcohol can be reacted with an esterification promotion agent such as methyl chloroformate, ethyl chloroformate, z ' s ⁇ -butyl chloroformate, and the like, and a base such as N-methylmorpholine and the like, to provide a mixed anhydride intermediate which, when reacted with an alcohol such as methanol, ethanol, or trifluoroethanol, provides a compound having structural formula (10).
  • an esterification promotion agent such as methyl chloroformate, ethyl chloroformate, z s ⁇ -butyl chloroformate, and the like
  • a base such as N-methylmorpholine and the like
  • a prefe ⁇ ed second esterifying agent for the practice of step (1) is methanol and sulfuric acid.
  • esterases useful for the practice of step (m) are Amano PS 30 Lipase, Atnano AY Candida Cylindracea, Aspergillus niger lipase, Aspergillus oryza protease, Alcaligenes species lipase, Aspergillus species protease, Bacillus species protease, Candida antartica "A” lipase, Candida antartica “B” lipase, Candida lipolytica lipase, Candida Rugosa esterase, Candida Rugosa lipase, ChiroCLEC-CR, ChiroCLEC-BL, ChiroCLEC-PC, ChiroCLEC-EC, alpha-crymotrypsin, Humicola lanuginosa lipase, Mucor melhel lipase, Papain, PeptiCLEC-TR, Penicillin acylase, Pig Liver enzyme, Porcine Liver esterase, Porcine Pancreatic lipase, Pse
  • Prefe ⁇ ed esterases for the practice of step (1) are Candida Rugosa lipase, Pig Liver enzyme, Amano PS 30 Lipas, Amano AY Candida Cylindracea, Porcine Pancreatic lipase, and Rhizopus Arrhizus Lipase Type XI.
  • a more preferred esterase for the practice of step (m) is Candida Rugosa Lipase.
  • the esterase concentration is between about 20 mg per mL and about 40 mg per mL.
  • the esterase concentration is about 36 mg per mL.
  • the pH of the solution is between about 5.5 and about 8.5. In a more prefe ⁇ ed embodiment for the practice of this step, the pH is about 8.
  • Step (m) is conducted at a temperature of between about 20 °C and about 50 °C in a solvent such as acetone, acetonitrile, a Cj-Cs alcohol such as methanol, ethanol, and ⁇ -propanol, dimethylsulfoxide, dioxane, heptane, hexane, methylethyl ketone, tetrahydrofuran, toluene, water, or a mixture thereof.
  • a solvent such as acetone, acetonitrile, a Cj-Cs alcohol such as methanol, ethanol, and ⁇ -propanol, dimethylsulfoxide, dioxane, heptane, hexane, methylethyl ketone, tetrahydrofuran, toluene, water, or a mixture thereof.
  • step (m) is conducted at a temperature of about 37 °C in essentially a mixture of water and acetone.
  • third reducing agents useful for the practice of step (n) are borane dimethylsulfide, borane-THF, sodium borohydride and iodine, aluminum hydride, aluminum hydride triethylamine, di( ⁇ O-butyl)aluminum hydride, zso-propoxyaluminum hydride, tert-butoxyaluminum hydride, di(tert-butoxy)aluminum hydride, lithium aluminum hydride, lithium aluminum hydride-N-methylpyrrolidine, sodium aluminum hydride, sodium diethylaluminum hydride, bis(2-methoxyethoxy)aluminum hydride, and lithium di(z ' ,so-butyl)(butyl)aluminum hydride.
  • step (n) The choice of third reducing agents for the practice of step (n) depends on the intermediate.
  • An intermediate having structural formula (11-a) will be more efficiently reduced with a borane agent while an intermediate having formula (11 -b) will be more efficiently reduced with an aluminum hydride agent.
  • the product of step (m) is a compound having formula (1 1-a)
  • the third reducing agent is borane dimethylsulfide.
  • Step (n) is conducted at a temperature between about 0 °C and about 50 °C in a solvent such as acetone, acetonitrile, a -C5 alcohol such as methanol, ethanol, and fso-propanol, dichloromethane, dimethyl sulfide, dimethylsulfoxide, diethyl ether, dioxane, heptane, hexane, methylethyl ketone, tetrahydrofuran, toluene, water, or a mixture thereof.
  • a solvent such as acetone, acetonitrile, a -C5 alcohol such as methanol, ethanol, and fso-propanol, dichloromethane, dimethyl sulfide, dimethylsulfoxide, diethyl ether, dioxane, heptane, hexane, methylethyl ketone, tetrahydrofur
  • step (n) is conducted in essentially a mixture of dichloromethane and dimethyl sulfide at a temperature of about 25 °C.
  • the compound having structural formula (12) is useful as an intermediate for making a compound having structural formula (15) (15), in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyalkyl, or aryl-(C 2 -C 4 -alkyl);
  • L 1 is N(R 7 ), O, S, S(O), or SO 2 ;
  • R is aryl, furanyl, or, thienyl in which the aryl, the furanyl, and the thienyl are unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and ⁇
  • R is hydrogen, alkyl, aryl, or ? ⁇ r ⁇ -toluenesulfonyl.
  • steps (p) and (q) are conducted in situ.
  • oxidants useful for the practice of step (p) are an activated dimethyl sulfoxide agent such as dimethylsulfoxide and oxalyl chloride, dimethylsulfoxide- SO3 pyridine, tetrapropylammonium perruthenate, 2,2,6,6-tetramethyl- 1 -piperidinyloxy, and the like.
  • first additives useful for the practice of step (p) are sodium hypochlorite/sodium bromide, potassium hypochlorite/potassium bromide, sodium hypochlorite/potassium bromide, potassium hypochlorite/sodium bromide, /V-methylmorpholine-/V-oxide, and the like.
  • the oxidant is an activated dimethyl sulfoxide agent, and the first additive is omitted.
  • the oxidant is dimethylsulfoxide S ⁇ 3 pyridine.
  • second bases useful for the practice of step (p) are diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, l,8-diazobicyclo[5.4.0]undec-7-ene, l,5-diazobicyclo[4.3.0]non-5-ene, 1-methylpiperidine, pyrazine, pyridazine, pyrimidme, pyridine, tetramethylenediamino- methane, tributylamine, triethylamine, and tripropylamine.
  • the second base is triethylamine.
  • Step (p) is conducted at a temperature between about -10 °C and about 30 °C in a solvent such as chloroform, dichloromethane, diethyl ether, dioxane, ethyl acetate, dimethylsulfoxide, N/V-dimethylformamide, w ⁇ -propyl acetate, tetrahydrofuran, toluene, or a mixture thereof.
  • a solvent such as chloroform, dichloromethane, diethyl ether, dioxane, ethyl acetate, dimethylsulfoxide, N/V-dimethylformamide, w ⁇ -propyl acetate, tetrahydrofuran, toluene, or a mixture thereof.
  • step (p) is conducted in essentially dichloromethane and dimethylsulfoxide at a temperature of about 0 °C, after which the dimethylsulfoxide is substantially removed to provide the product of step (p) as a solution comprising between about 20% and about 40% by weight of the compound having structural formula (13) in dichloromethane.
  • the product is a solution comprising about 30% by weight of the compound having structural formula (13) in dichloromethane .
  • drying agents useful for the practice of step (q) are 3 A sieves, 4A sieves, anhydrous sodium sulfate, anhydrous magnesium sulfate, anhydrous potassium carbonate, and the like.
  • a prefe ⁇ ed drying agent for the practice of step (q) is anhydrous sodium sulfate.
  • first acid catalysts for the practice of step (q) are camphorsulfonic acid, acetic acid/sodium acetate, pyridiniumjc ⁇ ra-toluene sulfonate, and j ⁇ ra-toluenesulfonic acid.
  • a prefe ⁇ ed first acid catalyst for the practice of step (q) is pyridinium /? ⁇ r ⁇ -toluene sulfonate.
  • Step (q) is conducted at a temperature between about 0 °C and about 30 °C in a solvent such as chloroform, dichloromethane, diethyl ether, dimethylsulfoxide, dioxane, NN-dimethylformamide, ethyl acetate, w ⁇ -propyl acetate, tetrahydrofuran, toluene, ⁇ rt ⁇ -xylene, weto-xylene, ⁇ r -xylene, tetrahydrofuran, or a mixture thereof.
  • a solvent such as chloroform, dichloromethane, diethyl ether, dimethylsulfoxide, dioxane, NN-dimethylformamide, ethyl acetate, w ⁇ -propyl acetate, tetrahydrofuran, toluene, ⁇ rt ⁇ -xylene, weto-xylene, ⁇ r -xylene, te
  • step (q) is conducted at about 25 °C in essentially dichloromethane, after which the dichloromethane is substantially replaced with heptane to provide between about 40% and about 70% by weight of the compound having structural formula (15) in heptane.
  • the product is a solution comprising essentially about 50% by weight of the compound having structural formula (15) in heptane.
  • a fifth embodiment of this invention is disclosed a process for making substantially pure ( ⁇ )-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate comprising, in toto, the steps of:
  • steps (r), (s), (t), and (u) are conducted sequentially.
  • silating agents useful for the practice of step (r) are 1,1,1,3,3,3- o hexamethyldisilazane, a compound of formula Si(R ) 3 (C1) in which each R is independently selected from the group consisting of alkyl and unsubstituted aryl, N,O-bis(trimethylsilyl)acetamide, and the like.
  • a prefe ⁇ ed silating agent for the practice of step (r) is ( ⁇ )-l, 1,1 ,3,3,3- hexamethyldisilazane, which preferably is present between about 1 molar equivalent and about 2 molar equivalents per molar equivalent of the ( ⁇ )-4-amino-3-hydroxy- «-butyric acid.
  • the 1,1,1,3,3,3-hexamethyldisilazane is present in about 1.61 molar equivalents per molar equivalent of the ( ⁇ )-4-amino-3- hydroxy- «-butyric acid.
  • third bases useful or the practice of step (r) are diethylenediamine, diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, l,8-diazobicyclo[5.4.0]undec-7-ene, l,5-diazobicyclo[4.3.0]non-5-ene, 1-methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediammo- methane, tributylamine, triethylamine, and tripropylamine.
  • a prefe ⁇ ed third base for the practice of step (r) is pyridine, which preferably is present between about 0.01 to about 10 molar equivalents per molar equivalent of the ( ⁇ )-4-amino-3-hydroxy- «-butyric acid.
  • the pyridine is present in about 7.4 molar equivalents per molar equivalent of the ( ⁇ )-4-amino- 3-hydroxy-H-butyric acid.
  • Step (r) is conducted at a temperature between about 100 °C and about 150 °C in a solvent such as toluene, ⁇ rt ⁇ -xylene, wet ⁇ -xylene, /? ⁇ r ⁇ -xylene, or a mixture thereof.
  • step (r) is conducted at about 130 °C to about 140 °C in essentially a mixture comprising ⁇ rt ⁇ -xylene, meta-xylene, and /j ⁇ r -xylene, after which the solvent is substantially removed.
  • tert-butylcarbonyloxy-introducing agents useful for the practice of step (s) are di-tert-butyl dicarbonate, l-(tert-butoxycarbonyl)-2-tert-butyl-3-methyl-4- imidazolidinone, (2-tert-butoxycarbonyloxyimino)-2-phenylacetonitrile), and the like.
  • a preferred tert-butylcarbonyloxy-introducing agent for the practice of step (s) is di-tert-butyl dicarbonate, which preferably is present in about 0.9 to about 1.5 molar equivalents per molar equivalent of the ( ⁇ )-tert-butyl-4-hydroxy-2-oxo- py ⁇ olidinecarboxylate.
  • the di-tert-butyl dicarbonate is present in about 1.2 molar equivalents per molar equivalent of the ( ⁇ )-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate.
  • the 4-dimethylaminopyridine in step (s) is present in about 0.01 to about 0.1 molar equivalents per molar equivalent of the ( ⁇ )-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate. In a more preferred embodiment of this step, the 4-dimethylaminopyridine is present in about 0.05 molar equivalents per molar equivalent of the ( ⁇ )-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate.
  • Step (s) is conducted at a temperature between about -10 °C and about 30 °C in a solvent such as dioxane, ethyl acetate, z ' so-propyl acetate, tetrahydrofuran, or a mixture thereof.
  • a solvent such as dioxane, ethyl acetate, z ' so-propyl acetate, tetrahydrofuran, or a mixture thereof.
  • step (s) is conducted at about 0 °C to about 25 °C in tetrahydrofuran, zs ⁇ -propyl acetate, or a mixture thereof. In a more prefe ⁇ ed embodiment, step (s) is conducted at about 0 °C to about 25 °C in tetrahydrofuran.
  • step (s) is conducted at about 0 °C to about 25 °C in fso-propyl acetate.
  • desilylating agents useful for the practice of step (t) are 2,3-dichloro-
  • a preferred desilylating agent for the practice of step (t) is triethylamine-trihydrofluoride.
  • Step (t) is conducted at a temperature between about -10 °C and about 30 °C in a solvent such as dioxane, ethyl acetate, z ' s ⁇ -propyl acetate, tetrahydrofuran, or a mixture thereof.
  • a solvent such as dioxane, ethyl acetate, z ' s ⁇ -propyl acetate, tetrahydrofuran, or a mixture thereof.
  • step (t) is conducted at about 0 °C to about 25 °C in tetrahydrofuran, ts ⁇ -propyl acetate, or a mixture thereof.
  • step (t) is conducted at about 0 °C to about 25 °C in tetrahydrofuran.
  • step (t) is conducted at about 0 °C to about 25 °C in w ⁇ -propyl acetate.
  • the practice of step (u) comprises isolation of the substantially pure ( ⁇ )-tert-butyl-4-hydroxy-2-oxo-py ⁇ olidinecarboxylate by precipitation of the same from either essentially tetrahydrofuran or essentially zs ⁇ -propyl acetate.
  • step (u) further comprises isolation of additional substantially pure ( ⁇ )-tert-butyl-4-hydroxy-2-oxo- py ⁇ olidinecarboxylate by treatment of the tetrahydrofuran or the zs ⁇ -propyl acetate with heptane and cooling the resulting solution to a temperature of about 0 °C to precipitate the additional substantially pure ( ⁇ )-tert-butyl-4-hydroxy-2-oxo-pyrrolidine.
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
  • R is alkyl, cycloalkyalkyl, or aryl-(C 2 -C 4 -alkyl);
  • L 1 is N(R 7 ), O, S, S(O), or SO 2 ;
  • R is aryl, furanyl, or thienyl, in which the aryl, the furanyl, and the thienyl are unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and ⁇ R is hydrogen, alkyl, aryl, or ⁇ r ⁇ -toluenesulfonyl.
  • a process for making a compound having structural formula (19-a) from the compound having structural formula (15-a) and the ( ⁇ )-tert-butyl-4-hydroxy-2-oxo-py ⁇ olidine-carboxylate comprising, in toto, the steps of: (v) reacting the ( ⁇ )-tert-butyl-4-hydroxy-2-oxo-py ⁇ olidinecarboxylate, a fourth base, and a compound having structural formula (16)
  • R is alkyl, haloalkyl, and aryl, in which the aryl is unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and X 1 is Br, Cl, or OSO -R 9 , a prefe ⁇ ed embodiment of which is methanesulfonyl chloride, to provide tert-butyl 2-oxo-3-pyrroline carboxylate;
  • each R is independently selected from the group consisting of alkyl and unsubstituted aryl, a prefe ⁇ ed embodiment of which is tert-butyldimethylsilyl trifluoromethanesulfonate, to provide a compound having structural formula (18)
  • step (x) reacting the product of step (w), a second acid, and a substantially enantiomerically enriched compound having the structural formula (15-a)
  • steps (v) and (w) are conducted in situ, steps
  • Examples of fourth bases usefiil for the practice of step (v) are diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, 1 ,8-diazobicyclo[5.4.0]undec-7-ene, 1 ,5-diazobicyclo[4.3.0]non-5-ene, 1 -methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediamino- methane, tributylamine, triethylamine, tripropylamine, and the like.
  • a prefe ⁇ ed fourth base for the practice of step (v) is triethylamine.
  • Step (v) is conducted at a temperature between about -10 °C and about 20 °C in a solvent such as carbon tetrachloride, chloroform, dichloromethane, dioxane, tetrahydrofuran, or a mixture thereof.
  • a solvent such as carbon tetrachloride, chloroform, dichloromethane, dioxane, tetrahydrofuran, or a mixture thereof.
  • step (v) is conducted at about 0 °C in essentially tetrahydrofuran, after which the tetrahydrofuran is substantially replaced with heptane.
  • Examples of fifth bases useful for the practice of step (w) are diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, l,8-diazobicyclo[5.4.0]undec-7-ene, l,5-diazobicyclo[4.3.0]non-5-ene, 1-methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediamino- methane, tributylamine, triethylamine, and tripropylamine, and the like.
  • a prefe ⁇ ed fourth base for the practice of step (w) is triethylamine.
  • Step (w) is conducted at a temperature between about -10 °C and about 20 °C in a solvent such as carbon tetrachloride, chloroform, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
  • a solvent such as carbon tetrachloride, chloroform, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
  • step (w) is conducted at about 0 °C in essentially heptane and dichloromethane, after which the dichloromethane is substantially removed.
  • second acids useful for the practice of step (x) are boron trifluoride diethyletherate, copper(II) bis(trifluoromethanesulfonate), trifluoromethanesulfonic acid, titanium r ' s ⁇ -propoxide, titanium tetrachloride, trimethylsilyltrifluoromethane sulfonate, tributylsilyltrifluoromethane sulfonate, ytterbium tetrakis(trifluoromethanesulfonate), zinc chloride, and the like.
  • a prefe ⁇ ed second acid for the practice of step (x) is trifluoromethanesulfonic acid.
  • Step (x) is conducted at a temperature between about -50 °C and about -30 °C in a solvent such as acetonitrile, chloroform, carbon tetrachloride, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
  • a solvent such as acetonitrile, chloroform, carbon tetrachloride, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
  • step (x) is conducted at about -40 °C in essentially heptane and tetrahydrofuran.
  • Step (y) is conducted at a temperature between about -50 °C and about -30 °C in a solvent such as acetonitrile, chloroform, carbon tetrachloride, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
  • a solvent such as acetonitrile, chloroform, carbon tetrachloride, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
  • step (y) is conducted at about -40 °C in essentially heptane and tetrahydrofuran.
  • step (z) the tetrahydrofuran is substantially replaced with heptane to precipitate a substantially pure compound having structural formula (19-a), which is then isolated with a diastereomeric excess greater than about 90: 1.
  • step (z) the compound having structural formula (19-a) is isolated with a diastereomeric excess greater than about 99: 1.
  • a compound having structural formula (19) is useful as an intermediate for making a compound having structural formula (24)
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
  • R is alkyl, cycloalkyalkyl, or aryl-(C 2 -C -alkyl);
  • R is methyl, ethyl, ⁇ -propyl, or vinyl.
  • a seventh embodiment of this invention therefore, is disclosed a process for making a compound having structural formula (24) from the compound having structural formula (19) comprising, in toto, the steps of:
  • conjugate addition agent comprising a mixture of compounds having structural formula (20-Z)
  • (20-E) in which the (20-Z)/(20-E) ratio in the mixture is about 97:3, and in which Q is Li, Mg-Cl, Mg-Br, or Mg-I, and, optionally, a second additive at a temperature between about -50 °C and about -30 °C about to provide a compound having structural formula (21)
  • step (bb) reacting the product of step (aa) and a third acid to provide a compound having the structural formula (22) or a salt thereof, a prefe ⁇ ed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (22-a)
  • step (cc) reacting the product of step (bb), an acetylating agent, and a sixth base to provide a compound having the structural formula (23)
  • step (dd) reacting the product of step (cc), a tert-butylcarbonyloxy-introducing agent, a seventh base, and 4-dimethylaminopyridine to provide the compound having formula (24), a prefe ⁇ ed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (24-a)
  • step (ee) optionally isolating the product of step (dd).
  • steps (aa), (bb), (cc), (dd), and (ee) are conducted in situ.
  • step (aa) examples of second additives useful for the practice of step (aa) are compounds
  • the second additive is employed, is trimethylsilyl chloride, and is present in about 0.5 to about 4 molar equivalents per molar equivalent of the compound having structural formula (19). In a more preferred embodiment of this step, the second additive is present in about 3 molar equivalents per molar equivalent of the compound having structural formula (19).
  • step (aa) is conducted at about -25 °C in a solvent such as acetonitrile, chloroform, dichloromethane, ethyl acetate, z ' s ⁇ -propyl acetate, tetrahydrofuran, toluene, or a mixture thereof.
  • step (aa) is conducted at about -25 °C in essentially tetrahydrofuran and toluene.
  • the conjugate addition agent used for the practice of step (aa) is made by reacting a mixture, said mixture comprising a precursor compound having structural formula (20-2?)
  • the (20-2?)/(20-E p ) ratio in the mixture is about 97:3, and in which Q is Li, Mg-Cl, Mg-Br, or Mg-I, a cuprous adjuvant, and optionally, a ligand selected from the group comprising tri-n-butylphosphine, tri-w ⁇ -butylphosphine, and tri-n-pentylphosphine.
  • cuprous adjuvant useful for the practice of step (aa) are copper(I) bromide, copper(I) bromide-dimethyl sulfide, copper(I) chloride, copper(I) bromide, copper(I) iodide, copper(I) cyanide, copper(I) tert-butoxide, copper(I) thiophenoxide, copper(I) thioisocyanate, copper(I) acetylide, copper(I) 3,3-dimethyl-l-butynide, copper(I) 1 -pentynide, and the like.
  • the ligand is omitted and the cuprous adjuvant is copper(I) bromide-dimethyl sulfide complex, which is present in about 0.05 molar equivalents to about 1.2 molar equivalents per molar equivalent of the compound having structural formula (19).
  • the cuprous adjuvant is present in about 0.5 molar equivalents per molar equivalent of the compound having structural formula (19).
  • the 97:3 (20-Z)/(20-E) mixture used for the practice of step (aa) is present in about 0.9 molar equivalents to about 3.5 molar equivalents per molar equivalent of the compound having structural formula (19).
  • the 97:3 (20-2)/(20-E) mixture is present in about 3 molar equivalents per molar equivalent of the compound having structural formula (19).
  • step (bb) examples include hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, trifluoroacetic acid, /> ⁇ r ⁇ -toluenesulfonic acid, pyridinium ⁇ r ⁇ -toluenesulfonic acid, camphorsulfonic acid, and the like.
  • the third acid is hydrochloric acid.
  • Step (bb) is conducted at a temperature between about -10 °C and about -30 °C in a solvent such as ethyl acetate, z ' s ⁇ -propyl acetate, tetrahydrofuran, toluene, water, or a mixture thereof.
  • a solvent such as ethyl acetate, z ' s ⁇ -propyl acetate, tetrahydrofuran, toluene, water, or a mixture thereof.
  • step (bb) is conducted at a temperature of about -20 °C in essentially tetrahydrofuran, toluene, and water.
  • acetylating agents useful for the practice of step (cc) are acetic anhydride, acetyl chloride, acetyl bromide, and the like.
  • the acetylating agent is acetic anhydride.
  • sixth bases for the practice of step (cc) are lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, diethylenediamine, diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, 1 ,8-diazobicyclo[5.4.0]undec-7-ene, 1 ,5-diazobicyclo[4.3.0]non- 5-ene, 1-methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediaminomethane, tributylamine, triethylamine, tripropylamine, and the like.
  • the sixth base is sodium hydroxide.
  • Step (cc) is conducted at a temperature between about 0 °C and about 35 °C in a solvent selected from the group comprising chloroform, dichloromethane, tetrahydrofuran, toluene, water, or a mixture thereof.
  • step (cc) is conducted at about 25 °C in essentially water.
  • tert-butylcarbonyloxy-introducing agents useful for the practice of step (dd) are di-tert-butyl dicarbonate, l-(tert-butoxycarbonyl)-2-ter/-butyl-3-methyl-4- imidazolidinone, (2-tert-butoxycarbonyloxyimino)-2-phenylacetonitrile), and the like.
  • the tert-butylcarbonyloxy- introducing agent is di-tert-butyl dicarbonate.
  • Examples of seventh bases useful for the practice of step (dd) are diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, 1 ,8-diazobicyclo[5.4.0]undec-7-ene, 1 ,5-diazobicyclo[4.3.0]non-5-ene, 1 -methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediaminomethane, tributylamine, triethylamine, tripropylamine, and the like.
  • the seventh base is triethylamine.
  • Step (dd) is conducted at a temperature between about 0 °C and about 35 °C in a solvent such as acetonitrile, ethyl acetate, w ⁇ -propyl acetate, tetrahydrofuran, toluene, water, or a mixture thereof.
  • a solvent such as acetonitrile, ethyl acetate, w ⁇ -propyl acetate, tetrahydrofuran, toluene, water, or a mixture thereof.
  • step (dd) is conducted at about 25 °C in essentially tetrahydrofuran.
  • step (ee) the tetrahydrofuran solution is mixed first with z ' so-propyl acetate, then with heptane, to crystallize the compound having structural formula (24).
  • a compound having structural formula (24) is useful as an intermediate for making a compound having structural formula (28)
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyalkyl, or aryl-(C 2 -C -alkyl); R is methyl, ethyl, zs ⁇ -propyl, or vinyl; and
  • R is hydrogen or alkyl.
  • step (gg) optionally reacting the product of step (ff), a -C 5 alcohol, a trialkylorthoformate, and a second acid catalyst to formula (26)
  • R , 11 i •s methyl, ethyl, propyl, or z ' so-propyl a prefe ⁇ ed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula
  • step (26-a) and a more preferred embodiment of which is substantially pure, diastereomerically enriched tert-butyl (2R,3S)-2-((lR,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-5-methoxy-3- (( 1 Z)- 1 -propenyl)- 1 -py ⁇ olidinecarboxylate; (hh) reacting the product of step (ff) or step (gg), a cyanide-donating agent, and a fourth acid to provide a compound having structural formula 27
  • step (ii) reacting the product of step (hh), a -C 5 alcohol, and a fifth acid to provide the compound having structural formula (28), a prefe ⁇ ed embodiment of which is a compound having the absolute stereochemistry illustrated by a
  • step (gg) is conducted, and steps (ff), (gg), (hh), and (ii) are conducted in situ.
  • Examples of fourth reducing agents useful for the practice of step (ff) are lithium borohydride, sodium borohydride, potassium borohydride, lithium di(z ' s ⁇ -butyl)aluminum hydride, lithium triethylborohydride, bis(2-methoxyethoxy)aluminum hydride, lithium tri- seobutylborohydride, potassium tri-sec-butylborohydride, lithium aluminum hydride-N- methylpyrrolidine, and the like.
  • the fourth reducing agent is lithium triethylborohydride.
  • Step (ff) is conducted at a temperature between about -20 °C and about 25 °C in a solvent such as chloroform, dibutylether, dichloromethane, diethylether, 1 ,2-dimethoxyethane, dioxane, hexane, heptane, tetrahydrofuran, toluene, or a mixture thereof.
  • a solvent such as chloroform, dibutylether, dichloromethane, diethylether, 1 ,2-dimethoxyethane, dioxane, hexane, heptane, tetrahydrofuran, toluene, or a mixture thereof.
  • step (ff) is conducted at about -15 °C to about 17 °C in essentially tetrahydrofuran.
  • Examples of -C 3 alcohols useful for the practice of step (gg) are methanol, ethanol, propanol, z ' so-propanol, and the like.
  • the -C 3 alcohol is methanol.
  • trialkylorthoformates useful for the practice of step (gg) are trimethylorthoformate, triethylorthoformate, tripropylorthoformate, triisopropylorthoformate, and the like.
  • the trialkylorthoformate is trimethylorthoformate .
  • second acid catalysts for the practice of step (gg) are pyridinium /> ⁇ ra-toluenesulfonate,/?-zra-toluenesulfonic acid, camphorsulfonic acid, sulfuric acid, methanesulfonic acid, and the like.
  • the second acid catalyst is camphorsulfonic acid.
  • Step (gg) is conducted at a temperature between about 0 °C and about 30 °C in a solvent such as methanol, ethanol, H-propanol, and ⁇ -propanol.
  • step (gg) is conducted at about 25 °C in essentially methanol.
  • cyanide-donating agents useful for the practice of step (hh) are sodium cyanide, trimethylsilylcyanide, tert-butyldimethylsilyl cyanide, zinc cyanide, diethylaluminum cyanide, and the like.
  • the cyanide-donating agent is trimethylsilylcyanide.
  • fourth acids useful for the practice of step (hh) are aluminum chloride, boron trifluoride-diethyletherate, diethylaluminum chloride, magnesium bromide diethyletherate tin(IV) chloride, titanium(IV) chloride, titanium(IV) tris(chloro)/5 ⁇ -propoxide, titanium(IN) bis(chloro)diisopropoxide, trifluoromethanesulfonic acid, tert-butyldimethylsilyl trifluoromethanesulfonate, triisopropylsilyl trifluoromethanesulfonate, trimethylsilyl trifluoromethanesulfonate, and triethylsilyl trifluoromethanesulfonate.
  • the fourth acid is trifluoromethanesulfonic acid.
  • Step (hh) is conducted at a temperature between about -50 °C and about 0 °C in a solvent such as acetonitrile, dichloromethane, dibutylether, diethylether, tetrahydrofuran, toluene, or a mixture thereof.
  • a solvent such as acetonitrile, dichloromethane, dibutylether, diethylether, tetrahydrofuran, toluene, or a mixture thereof.
  • step (hh) is conducted at about -40 °C in essentially acetonitrile.
  • Examples of fifth acids useful for the practice of step (ii) are hydrogen chloride/hydrochloric acid, hydrogen bromide/hydrobromic acid, sulfuric acid, trifluoromethanesulfonic acid, and the like.
  • the fifth acid is hydrogen chloride/hydrochloric acid.
  • Step (ii) is conducted at a temperature beginning between about -50 °C and about -20 °C and ending between about 80 °C and about 90 °C in methanol, ethanol, propanol, z ' s ⁇ -propanol, butanol, 1 -methyl- 1-butanol, 2-methyl-l-butanol, 1,1 -dimethyl- 1-butanol, pentanol, 1 -methyl- 1-butanol, 2-methyl-l-butanol, 3-methyl-l -butanol, 1 -ethyl- 1 -propanol, or 2-ethyl-l -propanol.
  • step (ii) is conducted initially at about -30 °C, then at about 25 °C for about one hour, then at about 90 °C for about eight hours in essentially z ' s ⁇ -propanol.
  • step (jj) comprises isolating the compound having formula (28), or a therapeutically acceptable salt thereof, by crystallization.
  • the compound having formula (28) is isopropyl (2R,5R)-5-((lR,25)-l-(acetylamino)-2-methoxy-2- methylpentyl)-4-((lZ)-l-propenyl-2 -py ⁇ olidinecarboxylate and is isolated by crystallization of its ⁇ ra-toluenesulfonate salt.
  • the crystallization comprises mixing a solution comprising essentially isopropyl (2R,5R)-5- (( 1 R,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-4-(( 1 Z)- 1 -propenyl)-2- py ⁇ olidinecarboxylate in z ' so-propyl acetate and a solution comprising essentially ra-toluenesulfonic acid monohydrate in wo-propyl acetate.
  • the crystallization of isopropyl (2R,5R)-5-((lR,25)-l-(acetylamino)-2-methoxy-2- methylpentyl)-4-(( 1 Z)- 1 -propenyl)-2 -py ⁇ olidinecarboxylate, /? ⁇ r ⁇ -toluenesulfonate is conducted at a solution temperature of between about 40 °C and about 70 °C, a prefe ⁇ ed embodiment of which is between about 50 °C and about 60 °C, in which the temperature of the solution is lowered to about 25 °C at a rate of about 5 °C per hour to precipitate the isopropyl (2R,5R)-5-((lR,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-4-(( 1Z)- 1 - propenyl)-2-pyrrolidine
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
  • R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; 4 ⁇
  • R is alkyl, cycloalkyalkyl, or aryl-(C 2 -C 4 -alkyl);
  • R is methyl, ethyl, iso-propyl, or vinyl
  • R is alkoxy alkoxycarbonyl, and hydroxy
  • R , 14 is hydrogen or tert-butoxycarbonyl
  • R , 15 is hydrogen or acetyl, with the proviso that R is alkoxycarbonyl only for the compound having structural formula (30-a), preferred embodiments of which include a compound having structural formula (29) or (29-a) in which R 1 is alkyl; R 2 is
  • R is alkyl; R is hydrogen, and R is hydrogen; a compound having structural formula (29) or (29-a) in which R is alkyl; R is
  • R is alkyl; R is hydrogen, and R is acetyl;
  • R is alkyl;
  • R is alkyl;
  • R 4 is alkyl;
  • R 14 is tert-butoxycarbonyl, and
  • R 15 is acetyl;
  • R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is tert-butoxycarbonyl, and R is hydrogen;
  • R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is tert-butoxycarbonyl, and R is acetyl;
  • R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is hydrogen, and R is hydrogen;
  • R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is hydrogen, and R is acetyl;
  • R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is tert-butoxycarbonyl, and R is hydrogen;
  • R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is tert-butoxycarbonyl, and R is acetyl;
  • R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is hydrogen, and R is hydrogen;
  • R 1 • 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is hydrogen, and R is acetyl; and a compound having structural formula (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxycarbonyl; R is hydrogen, and R is acetyl, of which the more prefe ⁇ ed embodiments of the foregoing are the compound having structural formula (29) or (29-a) in which R 1 is alkyl; R 2 is alkyl; R is alkyl; R is hydrogen, and R is hydrogen;
  • R is alkyl; R is alkyl; R is alkyl; R is hydrogen, and R is acetyl;
  • R is alkyl;
  • R is alkyl;
  • R is alkyl;
  • R is tert-butoxycarbonyl, and
  • R is acetyl;
  • the term “substantially pure” means greater than 90% pure; preferably greater than 95% pure, and more preferably greater than 99% pure. It is also meant to be understood that the term “essentially,” in reference to a solvent or solvents, means greater than 90% of that solvent or solvents; preferably greater than 95% of that solvent or solvents, and more preferably greater than 99% of that solvent or solvents. It is also meant to be understood that many of the compounds of this invention contain one chiral carbon atom and exist as enantiomers in the (R) or (S) configuration or as racemic mixtures comprising varying amounts of one enantiomer over the other. Mixtures comprising equimolar amounts of enantiomers are racemic mixtures and are designated ( ⁇ ).
  • Mixtures comprising varying amounts of one enantiomer over the other are designated enantiomerically enriched with the enantiomer present in the higher amount.
  • the enantiomeric enrichment of a mixture can be determined by gas or liquid chromatography in a chiral environment such as, for example, a column packed with a chiral auxiliary.
  • Prefe ⁇ ed enantiomeric enrichment for the purpose of this invention is about 86-89% enantiomeric excess of one enantiomer over the other.
  • a more prefe ⁇ ed enantiomeric enrichment for the purpose of this invention is about 94-97% enantiomeric excess of one enantiomer over the other.
  • a still more prefe ⁇ ed enantiomeric enrichment for the purpose of this invention is a substantially enantiomerically enriched mixture in which there is greater than a 99% enantiomeric excess of one enantiomer over the other.
  • Prefe ⁇ ed diastereomeric enrichment for the purpose of this mvention is an isolated yield of about 93:7 to about 95:5 mixture of diastereomers.
  • a more preferred diastereomeric enrichment for the purpose of this invention is an isolated yield of about 99.1 :0.9 mixture of diastereomers. Because the diastereomers of this invention have different solubilities, they can be separated by column chromatography on silica gel as described in the 787 application or, more preferably, by crystallization.
  • the compound of this invention having structural formula (25) exists as anomers in which the chiral carbon atom of the py ⁇ olidine ring bearing the hydroxy group exists as an equilibrium mixture of (R) and (S) isomers at that chiral carbon atom.
  • More preferred geometric isomeric enrichment for the purpose of this invention is a ratio of about 98.8: 1.2 Z/E.
  • a still more prefe ⁇ ed geometric isomeric enrichment for the purpose of this invention is a ratio of about 99.3:0.7 Z/E.
  • Such preferred geometrically isomerically enriched compounds are defined as being substantially in the Z configuration.
  • the compounds of this invention can exist as therapeutically acceptable salts.
  • therapeutically acceptable salt means salts or zwitterionic forms of the compounds which are water or oil-soluble or dispersible, which are suitable for inhibition of neuraminidases without undue toxicity, irritation, and allergic response, which are commensurate with a reasonable benefit risk ratio, and which are effective for their intended use.
  • the salts can be prepared during the final isolation and purification of a compound having structural formula (28) by derivatization of the same as a salt such as citrate, aspartate, benzoate, benzenesulfonate, bisulfate, butyrate, camphorate, camphorsufonate, digluconate, formate, fumarate, glycerophosphate, hemisulfate, heptanoate, hexanoate, hydrochloride, hydrobromide, hydroiodide, lactate, maleate, mesitylenesulfonate, methanesulfonate, naphthylenesulfonate, nicotinate, oxalate, pamoate, pectinate, persulfate, 3-phenylpropionate, picrate, pivalate, propionate, succinate, tartrate, thiocyanate, trichloroacetic, trifluoroacetic, phosphate, glutamate, bi
  • the compound having structural formula (28) is prepared as the j? ⁇ r ⁇ -toluenesulfonate salt.
  • Example 1 methyl (2E)-2-methyl-2-pentenoate
  • (2E)-2-methyl-2-pentenoic acid (1027 g), triethylformate (1031 g), and concentrated H 2 SO 4 (24 mL) in methanol (3.23L) was sti ⁇ ed at reflux for 10 hours, cooled to ambient temperature, and treated with NaHCO 3 (76 g).
  • the methanol layer was isolated and distilled at 45 mm Hg to provide fractions which distilled at 38-42 °C and 68-72 °C, the latter of which provided 820 g of desired product.
  • Example 2 (2E)-2-methyl-2-penten- 1 -ol
  • IM diisobutylaluminum hydride in hexane (2.768Kg) at -60 °C was treated with Example 1 (230 g) over 45 minutes, sti ⁇ ed for 1 hour, warmed to ambient temperature, added to a slurry of ice (1.3Kg) and 50% (w/w) aqueous NaOH (1.3Kg) over 1 hour, sti ⁇ ed for 2 hours at 0 °C, and warmed to ambient temperature over 18 hours.
  • Example 3 3 ,4-anhvdro- 1 ,2-dideoxy-4-methyl-D-threo-pentitol
  • a slurry of powdered 4A sieves (81 g) in dichloromethane (2.7L) at -20 °C was treated sequentially with dimethyl D-tartrate (102.4 g), titanium z ' so-propoxide (159 g), and Example 2 (180 g) in dichloromethane (315 mL), sti ⁇ ed for 20 minutes, cooled to -40 °C, treated with pre-dried (4 A sieves) 5-6M tert-butyl hydroperoxide in decane (719 mL), sti ⁇ ed for 2 hours, treated with dimethyl sulfide (90 mL) and 30% (w/w) aqueous NaOH (750 mL), sti ⁇ ed for 2 hours, warmed to 15 °C, and treated with water (IL).
  • dimethyl D-tartrate
  • Example 4 (25)-2-methyl- 1 ,2-pentanediol
  • a solution of IM lithium aluminum hydride in THF (3.59L) at -40 °C was treated with a solution of Example 3 (104 g) in THF (300 mL) over 2 hours, warmed to ambient temperature over 18 hours, cooled to -20 °C, treated sequentially with water (100 mL), 15% (w/w) aqueous NaOH (100 mL), and water (150 mL), each over 1 hour, sti ⁇ ed for 2 hours while warming to 10 °C, filtered through diatomaceous earth (Celite ), and concentrated.
  • IM lithium aluminum hydride in THF (3.59L) at -40 °C was treated with a solution of Example 3 (104 g) in THF (300 mL) over 2 hours, warmed to ambient temperature over 18 hours, cooled to -20 °C, treated sequentially with water (100 mL), 15% (w/w) aque
  • the concentrate was fractionally distilled at 45 mm Hg to provide 105.1 g (50%, two steps) of the desired product (85-93% ee) as a fraction which distilled at 128-130 °C.
  • Example 5 ((((25)-2-methoxy-2-methylpentyl)oxy)methyl)benzene
  • a suspension of dry sodium hydride (prepared by washing 6.18 g of 60% oily sodium hydride with heptane (2x 200 mL)) in THF at 0 °C was treated sequentially with a solution of Example 4 (82.4 g) in THF (50 mL) over 30 minutes and benzyl bromide (90.6 mL) over 30 minutes, stirred for 12 hours at ambient temperature, cooled to 0 °C, treated with methyl iodide (272 mL), stirred for 18 hours at ambient temperature, and treated with water (500 mL) and methyl tert-butyl ether (500 mL).
  • the organic layer was isolated and concentrated.
  • the concentrate was treated sequentially with with ⁇ yV-dimethyl ethylenediamine (18.5 g), water (IL) and methyl tert-butyl ether (IL).
  • the organic layer was isolated, washed with IM HC1 (100 mL) and 3% (w/w) aqueous sodium chloride (200 mL) and concentrated to provide 145 g (93.5%) of the desired product, which was used directly in the next step.
  • Example 6 (25)-2-methoxy-2-methyl- 1 -pentanol
  • a solution of Example 5 (99.5 g) in THF (650 mL) at ambient temperature was treated with 5% palladium hydroxide on carbon (13 g), sti ⁇ ed under hydrogen at 40 pounds per square inch for 18 hours, and filtered through diatomaceous earth (Celite ).
  • the filtrate was treated with 5% palladium hydroxide on carbon (13 g), sti ⁇ ed under hydrogen at 40 pounds per square inch for 1 hour, filtered through diatomaceous earth (Celite ), and concentrated.
  • Examples 7-10 describe an alternate synthesis of Example 6.
  • Example 7 2-methoxy-2-methylpentanoic acid A solution of 2-pentanone (2Kg) and bromoform (61Kg) in methanol (6.3Kg) at 0 °C with overhead stirring was treated with a solution of potassium hydroxide (10.6Kg) in methanol (19Kg) over 5 hours, filtered, and concentrated. The concentrate was treated with 20%) (w/w) aqueous sodium hydroxide to pH 9.
  • Example 8 methyl 2-methoxy-2-methylpentanoate A solution of Example 7 (2.5Kg) in methanol (12L) at ambient temperature was treated with concentrated sulfuric acid (200 mL), heated to reflux for 16 hours, cooled to ambient temperature, treated with sodium bicarbonate (1.5Kg), and concentrated. The concentrate was dissolved in methyl tert-butyl ether (8L), extracted with water (4L) and saturated aqueous Na 2 CO 3 (100 mL), and concentrated. The concentrate was distilled at 50 mm Hg, and a fraction boiling at 90-95 °C was collected to provide 2.1 Kg (77%) of the ddeessiirreedd pprroodduucctt.. !!
  • Example 9 (25)-2-methoxy-2-methylpentanoic acid
  • Candida Ruglosa (20 g, 875 units/mg) was treated sequentially with 0.05M phosphate buffer (pH 8) and a solution of Example 8 (20 g) in acetone (50 mL), heated at 37 °C for 116 hours with a pH adjustment to 4.5-6 with 2M NaOH after 74 hours, acidified to pH 2 with 2M HCl, and extracted with ethyl acetate (500 mL).
  • This extract was extracted with 10% (w/w) aqueous Na 2 CO 3 (200 mL and 100 mL), and the combined aqueous extracts were acidified to pH 3 with concentrated HCl and extracted with methyl tert-butyl ether (300 mL). This extract was dried (Na 2 SO ), filtered, and concentrated to provide 8.5 g (93% recovery, >99% ee) of the desired product, which was used directly in t thhee nneexxtt sstteepp..
  • Example 10 (25)-2-methoxy-2-methyl- 1 -pentanol
  • a solution of Example 9 (507 g) in dichloromethane (3L) at 0 °C was treated with 10M borane-dimethyl sulfide (624 mL), sti ⁇ ed for 5 hours at ambient temperature, cooled to 0 °C to 5 °C, treated with 2M NaOH (3.3L), warmed to ambient temperature and stirred for several hours. The layers were separated, and the water layer was extracted with dichloromethane (2x 1.6L).
  • Example 11 (25)-2-methoxy-2-methylpentanal
  • a solution of Example 8 (19.21 g) and triethylamine (60 mL) in dichloromethane (40 mL) at 0 °C was treated with sulfur trioxide-pyridine (35 g) in DMSO (160 mL) over 2.5 hours, sti ⁇ ed for 30 minutes, and treated with 2M H 3 PO 4 (325 mL) over 30 minutes.
  • Example 12 ( 1 E,25)-2-methoxy-2-methylpentanal 5-tritylthioxime The solution of the 29.7% (w/w) solution of Example 11 in dichloromethane
  • Example 13 tert-butyl-4-hvdroxy-2-oxo-py ⁇ olidinecarboxylate
  • pyridine 125 mL
  • hexamethyldisilazane 71.5 mL
  • xylenes 250 mL
  • 4-dimethylaminopyridine (1.22 g) in THF (40 mL)
  • di-tert-butyldicarbonate 54.96 g) in THF (80 mL
  • stirred for 14 hours at ambient temperature treated with triethylamine trihydrofluoride (15 mL), sti ⁇ ed for 2 hours, treated with heptane, cooled to 3 °C, and filtered.
  • Example 14 tert-butyl 2-oxo-3-py ⁇ oline carboxylate
  • THF 31.26Kg
  • triethylamine 4.425Kg
  • methanesulfonyl chloride 2.32Kg
  • ethyl acetate 40L
  • the filtrate was washed with 15%> (w/w) aqueous NaCl (2x 13L), and the combined washings were extracted with isopropyl acetate (13.3L).
  • Example 14 (2.506Kg), dichloromethane (25L), and heptane (25.8L).
  • the resulting solution slurry was treated with triethylamine (4.5Kg), cooled to 0 °C, and treated with tert-butyldimethylsilyl trifluoromethanesulfonate (4.71 Kg) over 2 hours, sti ⁇ ed for 1 hour, treated with methanol (IL) over 10 minutes, sti ⁇ ed for an additional 20 minutes, concentrated to 20L with intermittent heptane treatment (3x 20L), filtered, concentrated to 7.913Kg, and treated with heptane (3.5Kg) to provide 11.41Kg of a 39.3% (w/w) solution of the desired product (96.5%), which was used directly in the next step.
  • IL methanol
  • Example 16 tert-butyl (2R)-2-(dR.25)-2-methoxy-2-methyl-l-(ftritylsulfanvnamino pentyl)-5-oxo- 2.5 -dihydro- 1-1 H-py ⁇ ole- 1 -carboxylate
  • iri heptane 2.534Kg
  • THF 14.54Kg
  • 320 g trifluoromethanesulfonic acid
  • additional trifluoromethanesulfonic acid 11 mL, 5.5 mL, and 22 mL
  • the solution was sti ⁇ ed for 1 hour at -40 °C, washed with 0.5M NaHCO 3 (16.3Kg) and brine (3.8Kg), treated with heptane (3.15Kg), and concentrated with intermittent heptane treatment (3.2Kg, 4.3Kg, 1.6Kg, and 5.6Kg) to keep its volume at 8L during the distillation.
  • a solid that precipitated from the mother liquor during the distillation was filtered and dried under vacuum at 50 °C to provide 1.353Kg (82%) of the diastereomerically enriched desired product. !
  • Example 17 The solution of Example 17 was cooled to -20 °C, treated sequentially with HCl gas (100 g) over 1 hour, sti ⁇ ed for an additional 10 minutes, treated with diatomaceous
  • Example 19 N-((lR.25)-2-methoxy-2-methyl-l-( ' (2R.35)-5-oxo-3-f(lZ)-l- propenyl) ⁇ y ⁇ olidinyl)pentyl)acetamide
  • the combined aqueous extracts from Example 18 were treated with 50%> (w/w) aqueous NaOH (17 mL) to pH 14 and acetic anhydride (16.62 g and 1.48 g), with additional 50%> NaOH added to maintain the pH of the solution at 12, stirred for 5 minutes, and treated with sodium chloride (7 g).
  • the organic layer was isolated, and the water layer was extracted with isopropyl acetate (2x 200 mL).
  • Example 21 2 1 anomeric tert-butyl (2R.35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5- hydroxy-3 -(( 1 Z)- 1 -propenyl)- 1 -py ⁇ olidinecarboxylate
  • Example 20 A solution of Example 20 (50.0 g) in THF (500 mL) at -13.5 °C with overhead
  • Example 22 tert-butyU2R.35)-2-((lR.25)-l-(acetylamino)-2-methoxy-2-methylpentyl -5-methoxy-3- (( 1 Z)- 1 -propenyl)- 1 -py ⁇ olidinecarboxylate
  • the solution of Example 21 was concentrated twice to 100 mL with a methanol treatment (500 mL) between the concentrations then concentrated to 176.1 g after a final methanol (500 mL) treatment.
  • the concentrate was treated with methanol (90 mL), trimethylorthoformate (50 mL), and camphor sulfonic acid (1.41 g), stirred for 1 hour, treated with 5% (w/w) aqueous KHCO 3 , and extracted with isopropyl acetate (IL).
  • the extract was washed with 23% (w/w) aqueous NaCl, concentrated twice to 150 mL with an intermittent acetonitrile treatment (500 mL), concentrated to 150.57 g after a acetonitrile (500 mL) treatment, and treated with acetonitrile (370 mL) to provide 435.5 g of a 11.2% (w/w) solution of the desired product (97.5%), which was used directly in the next step. !
  • Example 22 A solution 13% (w/w) of Example 22 in acetonitrile (153.66 g) was treated with acetonitrile (23.83 g), cooled to -20 °C, treated with trimethylsilylcyanide (15.19 g), cooled to -40 °C, treated with trifluoromethanesulfonic acid (10.95 g) over 30 minutes, stirred an additional 3 hours, and added to a mixture of 10%> (w/w) aqueous K 2 CO 3 (400 mL) containing 7.76 g NaOH and isopropyl acetate (400 mL).
  • the extract was separated, washed sequentially with 23% (w/w) aqueous NaCl and 23% (w/w) aqueous NaCl containing KH 2 PO 4 (2.82 g) and Na 2 HPO 4 -7H 2 O (7.12 g), concentrated to 50 mL with intermittent isopropyl alcohol treatment (3x 400 mL), and treated with isopropyl alcohol to provide 95.74 g of a 17.2% (w/w) solution of the desired product (86.9%), which was used directly in the next step.
  • Example 24 isopropyl (2R.5R)-5-(dR.25)-l-(acetylamino)-2-methoxy-2-methylpentvn-4-((lZ)-l- propenyl)-2-pyHolidinecarboxylate, para-toluenesulfonic acid salt
  • Example 23 A solution of 20% (w/w) of Example 23 in isopropyl alcohol (231.43 g) was treated with isopropyl alcohol (44.43 g), cooled to -30 °C, treated with HCl gas
  • the aqueous washings were combined and extracted with isopropyl acetate (160.9 g), and the combined organic extracts were washed with 20% (w/w) aqueous NaCl (300 g) and concentrated twice to one-quarter of their original volume with an intermittent isopropyl acetate treatment (374 g). This concentrate was filtered with isopropyl acetate (427 g) rinsing.
  • the filtrate was treated with isopropyl acetate (843.56 g), warmed to 50-60 °C, and treated with a solution ofp ⁇ ra-toluenesulfonic acid monohydrate (24.07 g) in isopropyl acetate (256.7 g) at 50-60 °C, sti ⁇ ed for 50 minutes, cooled to ambient tremperature at 5 °C/hour, and filtered with isopropyl acetate (2x 200 g) rinsing. The filtrant was dried under vacuum at 40 °C to provide 53.78 g (94.7%) of the desired product.

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Abstract

A process for the preparation of neuraminidase inhibitors having structural formula (28) or therapeutically acceptable salts thereof, in which R1 is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R2 is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R4 is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl); R10 is methyl, ethyl, iso-propyl, or vinyl; and R12 is hydrogen or alkyl and intermediates useful for the process are disclosed.

Description

PROCESS FOR THE PREPARATION OF SUBSTITUTED PYRROLIDINE NEURAMINIDASE INHIBITORS
Technical Field
This invention is directed to a process for making substituted pyrrolidine neuraminidase inhibitors and to intermediates which are useful in the process.
Background of the Invention
Drugs such as zanamivr (Relenza ) are known in the art as agents which inhibit neuraminidases and are therefore potentially useful for the treatment and prophylaxis of influenza (N EnglJ Med 2000; 343(18): 1282-9).
A novel series of substituted pyrrolidine inhibitors of neuraminidases is also disclosed in commonly owned, co-pending United States patent application serial No. 09/421,787, a subset series of which is illustrated by a compound having structural formula (28)
Figure imgf000002_0001
(28)
1 2 in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl); R is
12 methyl, ethyl, iso-propyl, or vinyl; and R is hydrogen or alkyl.
A more cost-effective preparation, however, is needed for the manufacture of the compounds of this subset series in the quantities required for clinical development. Disclosure of the Invention
This invention, therefore, is directed to a synthesis of inhibitors of neuraminidases in which column chromatographic purification is omitted; in which steps are conducted sequentially, in situ, and continuously; and in which critical reaction parameters such as agents employed and ratios of the same, solvents, temperatures, and times are optimized to provide a more cost-efficient synthesis than that disclosed in the 787 application.
The term "steps conducted sequentially" means conduction of a plurality of steps without work-up between the steps.
The term "steps conducted in situ" means conduction of a plurality of steps with a workup between the steps and during which the product remains in solution. Steps conducted in situ can be accompanied by solvent exchange, during which one solvent or solvents is substantially exchanged for another solvent or solvents and during which exchange the product remains in solution. The term "steps conducted continuously" means the conduction of a step followed by work-up and solvent removal before beginning a subsequent step.
It is meant to be understood that in the hierarchy of preferentially for the practice of this invention, methods comprising steps which are conducted sequentially are preferred over methods comprising steps conducted in situ, which are, in turn, preferred over methods comprising steps conducted continuously.
It is also meant to be understood also that the terms L , R -R , P , Q , X , each meant to represent groups of radicals, have the following meanings: "alkoxy" means an alkyl radical attached to the parent molecular group through an oxygen atom; "alkoxycarbonyl" means an alkoxy radical attached to the parent molecular group through a carbonyl; "alkyl" means a saturated, monovalent straight or branched hydrocarbon radical having one to six carbon atoms; "aryl" means a six-membered aromatic, carbocyclic ring which is unsubstituted or substituted by independent replacement of a hydrogen atom or atoms thereon by an alkyl, alkoxy, halo, or nitro radical; "arylalkyl" means an alkyl radical derivatized by the replacement of a hydrogen atom thereon by an aryl radical; "aryl-(C2-C4-alkyl)" means an alkyl radical having two, three, or four carbon atoms derivatized by the replacement of a hydrogen atom thereon by an aryl radical; "carbonyl" means -C(=O)-; "cycloalkyl" means a saturated, cyclic hydrocarbon radical having three to six carbon atoms; " cycloalkylalkyl" means an alkyl radical derivatized by replacement of a hydrogen atom thereon by a cycloalkyl radical; "halo" means a fluoride (F), chloride (Cl), or bromide (Br) radical; "haloalkyl" means an alkyl radical derivatized by independent replacement of one to six hydrogen atoms thereon by a halo radical; "hydroxy" means -OH; "nitro" means -NO2; and "vinyl" means -C(H)=C(H)2.
In a first embodiment of this invention, then, is disclosed a process for making a compound having structural formula (5)
R1 R2 OH0H
(5), in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; and
2 R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl, comprising the steps of: (a) reacting a compound having s
Figure imgf000004_0001
(1), a preferred embodiment of which is substantially pure
(2E)-2-methyl-2-pentenoic acid, a first acid, a first esterifying agent, and, optionally, a trialkylorthofoimate to provide a compound having structural formula (2)
in which
Figure imgf000004_0002
a preferred embodiment of which is substantially pure methyl (2E)-2-methyl-2-pentenoate;
(b) reacting the product of step (a) and a first reducing agent to provide a compound having structural formula (3)
Figure imgf000004_0003
(3), and a preferred embodiment of which is substantially pure
(2E)-2-methyl-2-penten- 1 -ol;
(c) reacting the product of step (b) and a titanium wø-propoxide-dialkyl tartrate complex;
(d) reacting the product of step (c) and tert-butyl hydroperoxide to provide a compound having structural formula (4)
Figure imgf000004_0004
(4), a preferred embodiment of which is a compound having the stereochemistry illustrated by a compound having structural formula (4-a)
Figure imgf000005_0001
and a more preferred embodiment of which is substantially pure, enantiomerically enriched 3 ,4-anhydro- 1 ,2-dideoxy-4-methyl-D-threo-pentitol ;
and
(e) reacting the product of step (d) and a second reducing agent to provide the compound having structural formula (5), a preferred embodiment of which is the compound having the stereochemistry illustrated by a compound having structural formula (5-a)
R1^^OH
Rz OH (5-a), and a more preferred embodiment of which is substantially pure, enantiomerically enriched
(2S)-2-methyl- 1 ,2-pentanediol;
and
(f) optionally isolating the compound having structural formula (5). In a preferred first embodiment, steps (c) and (d) are conducted sequentially, and steps (d) and (e) are conducted continuously.
Examples of first acids useful for the practice of step (a) include hydrochloric acid, perchloric acid, phosphoric acid, sulfuric acid, trifluoroacetic acid, and the like.
A preferred acid for the practice of step (a) is sulfuric acid. Examples of first esterifying agents useful for the practice of step (a) include ώo-butylene, a CpC4 alcohol such as methanol, ethanol, z'so-propanol, ter/-butyoxycarbonyl-2-( 1 -acetamido-2-methoxy-2-methyl)pentyl-3-(cis-propeny- 1 - yl)pyrrolidine-5-carboxylic acid tert-butyl ester, and the like.
A preferred first esterifying agent for the practice of step (a) is methanol. Examples of trialkylorthoformates useful for the practice of step (a) include trimethylorthoformate, triethylorthoformate, and tri-wo-propylorthoformate.
A preferred trialkylorthoformate for the practice of step (a) is trimethylorthoformate .
Step (a) is conducted at a temperature between about 25 °C and 100 °C in a C]-C5 alcohol solvent such as methanol, ethanol, tsø-propanol, «-butanol, and the like.
In a preferred embodiment, step (a) is conducted at about 60 °C in essentially methanol.
Examples of first reducing agents useful for the practice of step (b) include lithium borohydride, lithium borohydride pyrrolidine, lithium triethylborohydride, lithium triethylborohydride, potassium triethylborohydride, potassium tri(sec-butyl)borohydride, potassium triphenylborohydride, aluminum hydride, aluminum hydride triethylamine, di(zsø-butyl)aluminum hydride, isø-propoxyaluminum hydride, tert-butoxyaluminum hydride, di(tert-butoxy)aluminum hydride, lithium aluminum hydride, lithium aluminum hydride N-methylpyrrolidine, sodium aluminum hydride, sodium diethylaluminum hydride, bis(2-methoxyethoxy)aluminum hydride, lithium di(wo-butyl)aluminum hydride, and the like.
A preferred first reducing agent for the practice of step (b) is di(iso- butyl)aluminum hydride.
Step (b) is conducted at a temperature between about -60 °C and about -50 °C in a solvent such as diethyl ether, hexane, heptane, tetrahydrofuran, or a mixture thereof.
In a preferred embodiment, step (b) is conducted at about -60 °C in essentially hexane. In another part of the first embodiment of this invention, the titanium
/sø-propoxide dialkyl tartrate used for the practice of step (c) is prepared by reacting titanium wø-propoxide and a dialkyl tartrate.
Preferably, the dialkyl tartrate employed for the practice of step (c) is D-dimethyl tartrate, D-diethyl tartrate, or D-diisopropyl tartrate. More preferably the dialkyl tartrate employed for the practice of step (c) is
D-dimethyl tartrate.
Step (c) is conducted at a temperature between about -10 °C and about -30 °C in a solvent such as dichloromethane, chloroform, carbon tetrachloride, or a mixture thereof. In a preferred embodiment, step (c) is conducted at about -20 °C in essentially dichloromethane.
Step (d) is conducted at a temperature of between about -30 °C and about -50 °C in a solvent such as carbon tetrachloride, chloroform, decane, dichloromethane, hexane, heptane, pentane, or a mixture thereof.
In a preferred embodiment, step (d) is conducted at about -40 °C in essentially a mixture of decane and dichloromethane.
In another part of the first embodiment of this invention, both the titanium tsø-propoxide dialkyl tartrate complex and the tert-butyl hydroperoxide in steps (c) and (d), respectively, are each present in about 0.3 molar equivalents per molar equivalent of the compound having structural formula (3), and the compound having formula (4) has an enantiomeric excess of between about 86% and 89%. In a preferred embodiment of these steps, both the titanium wo-propoxide dialkyl tartrate complex and the tert-butyl hydroperoxide in steps (c) and (d), respectively, are each present in about 1.0 molar equivalent per molar equivalent of the compound having structural formula (3), and the compound having formula (4) has an enantiomeric excess of between about 94% and about 97%. Examples of second reducing agents useful for the practice of step (e) include borane dimethylsulfide, borane tetrahydrofuran, borane and boron trifluoride diethyletherate, borane sodium borohydride, lithium borohydride, lithium borohydride pyπolidine, lithium triethylborohydride, lithium triethylborohydride, potassium triethylborohydride, potassium tri(.sec-butyl)borohydride, potassium triphenylborohydride, aluminum hydride, aluminum hydride-triethylamine, di(wo-butyl)aluminum hydride, wo-propoxyaluminum hydride, tert-butoxyaluminum hydride, di(tert-butoxy)aluminum hydride, lithium aluminum hydride, lithium aluminum hydride-N-methylpyrrolidine, sodium alummum hydride, sodium diethylaluminum hydride, bis(2-methoxyethoxy)aluminum hydride, lithium di(i5o-butyl)(butyl)aluminum hydride, and the like.
A prefeπed second reducing agent for the practice of step (e) is lithium aluminum hydride.
Step (e) is conducted at a temperature between about -30 °C and about -50 °C in a solvent such as diethylether, dioxane, tetrahydrofuran, or a mixture thereof. In a prefeπed embodiment, step (e) is conducted at about -40 °C in essentially tetrahydrofuran.
In another prefeπed first embodiment, step (f) is conducted, and the product of step (e) is isolated by distillation.
A compound having structural formula (5) is useful as an intermediate for making a compound having structural formula (12)
Figure imgf000007_0001
(12), in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; and R is alkyl, cycloalkyalkyl, or aryl-(C2-C -alkyl). In a second embodiment of this invention, therefore, is disclosed a process for making a compound having structural formula (12) from the compound having structural formula (5) comprising, in toto, the steps of: (g) reacting the compound having structural formula (5)
R1^^OH
R2 OH (5), a preferred embodiment of which is a compound having the stereochemistry illustrated by a compound having structural formula (5-a)
Figure imgf000008_0001
(5-a), and a more prefeπed embodiment of which is substantially pure, enantiomerically enriched
(2S)-2 -methyl- 1 ,2-pentanediol, a first base, and a selectively removable hydroxy protecting group precursor to provide a compound having structural formula (6)
Figure imgf000008_0002
(6), in which P is a selectively removable hydroxy protecting group, a preferred embodiment of which is a compound having the stereochemistry illustrated by a compound having structural formula (6-a)
Figure imgf000008_0003
(6- -a), and a more prefeπed embodiment of which is substantially pure, enantiomerically enriched
(2S)-1 i -(benzyloxy)-! 2-methyl-2-pentanol;
(h) reacting the product of step (g), an alkylating agent, and the first base to provide a compound having structural formula (7)
Figure imgf000008_0004
a prefeπed embodiment of which is a compound having the stereochemistry illustrated by a compound having structu
Figure imgf000009_0001
(7-a), and a more preferred embodiment of which is substantially pure, enantiomerically enriched
((((2S)-2-methoxy-2-methylpentyl)oxy)methyl)benzene;
(i) reacting the product of step (h) and a hydroxy protecting group removal agent to provide the compound having structural formula (12), a prefeπed embodiment of which is a compound having the stereochemistry illustrated by a compound having structural formula (12-a)
Figure imgf000009_0002
(12-a), a more prefeπed embodiment of which is a compound having the stereochemistry illustrated by a compound having structural formula (12-b),
Figure imgf000009_0003
(12-b), and a still more prefeπed embodiment of which is substantially pure, enantiomerically enriched
(2S)-2-methoxy-2-methyl- 1 -pentanol;
and
(j) optionally isolating the compound having structural formula (12). In a prefeπed second embodiment, steps (g) and (h) are conducted sequentially, and steps (h) and (i) are conducted continuously.
Examples of first bases useful for the practice of step (g) and step (h) include dibutyltin oxide, lithium diisopropylamide, sodium hydride, potassium hydride, lithium bis(trimethylsilylamide), sodium bis(trimethylsilylamide), potassium bis(trimethylsilylamide), lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, lithium tert-amylate, sodium tert-amylate, potassium tert-amylate, and the like.
A preferred first base for the practice of step (g) and step (h) is sodium hydride. Examples of selectively removable hydroxy protecting group precursors for the practice of step (g) include methoxymethyl bromide, methoxymethyl chloride, methylthiomethyl bromide, methylthiomethyl chloride,
(phenyldimethylsilyl)methoxymethyl bromide, (phenyldimethylsilyl)methoxymethyl chloride, benzyloxymethyl bromide, benzyloxymethyl chloride, αrα-methoxybenzyloxymethyl bromide, />αrα-methoxybenzyloxymethyl chloride, /? rα-nitrobenzyloxymethyl bromide, αra-nitrobenzyloxymethyl chloride, ørt/io-nitrobenzyloxymethyl bromide, ørtΛø-nitrobenzyloxymethyl chloride, (4-methoxyphenoxy)methyl bromide, (4-methoxyphenoxy)methyl chloride, tert-butoxymethyl bromide, tert-butoxymethyl chloride, 4-pentenyloxymethyl bromide, 4-pentenyloxymethyl chloride, siloxymethyl bromide, siloxymethyl chloride, 2-methoxyethoxymethyl bromide, 2-methoxyethoxymethyl chloride, 2,2,2-trichloroethoxymethyl bromide, 2,2,2-trichloroethoxymethyl chloride, bis(2-chloroethoxy)methyl bromide, bis(2-chloroethoxy)methyl chloride, 2-(trimethylsilyl)ethoxymethyl bromide, 2-(trimethylsilyl)ethoxymethyl chloride, 1-ethoxyethyl bromide, 1 -ethoxyethyl chloride, l-(2-chloroethoxy)ethyl bromide, l-(2-chloroethoxy)ethyl chloride, l-(2-(trimethylsilyl)ethoxy)ethyl bromide, 1 -(2-(trimethylsilyl)ethoxy)ethyl chloride, pαrα-methoxybenzyl bromide, Tjαra-methoxybenzyl chloride, 1 -methyl- 1 -methoxyethyl bromide, 1 -methyl- 1 -methoxyethyl chloride, 1 -methyl- 1 -benzyloxyethyl bromide, 1 -methyl- 1- benzyloxyethyl chloride, 1 -methyl- l-benzyloxy-2-fluoroethyl bromide, 1 -methyl- 1- benzyloxy-2-fluoroethyl chloride, 1 -methyl- 1 -phenoxyethyl bromide, 1 -methyl- 1- phenoxyethyl chloride, 2,2,2-trichloroethyl bromide, 2,2,2 -trichloroethyl chloride, benzyltrichloroacetimidate, 2-trimethylsilylethyl bromide, 2-trimethylsilylethyl chloride, 2-(benzylthio)ethyl bromide, 2-(benzylthio)ethyl chloride, 2-(phenylselenyl)ethyl bromide, 2-(phenylselenyl)ethyl chloride, allyl bromide, allyl chloride, propargy bromide, propargy chloride, benzyl bromide, benzyl chloride, 3,4-dimethoxybenzyl bromide, 3,4-dimethoxybenzyl chloride, ørt/zo-nitrobenzyl bromide, ørtλø-nitrobenzyl chloride, j7αra-nitrobenzyl bromide, /?αrø-nitrobenzyl chloride, /?αrø-halobenzyl bromide, /? ra-halobenzyl chloride, 2,6-dichlorobenzyl bromide, 2,6-dichlorobenzyl chloride, />αra-cyanobenzyl bromide, /?αrø-cyanobenzyl chloride, />αra-phenylbenzyl bromide, 2,6-difluorobenzyl bromide, jøαrø-acylaminobenzyl bromide, αrα-acylaminobenzyl chloride, para-azidόbenzyl bromide, /?αrø-azidobenzyl chloride, 4-azido-3-chlorobenzyl bromide, 4-azido-3-chlorobenzyl chloride, 2-trifluoromethylbenzyl bromide, 2-trifluoromethylbenzyl chloride, /?αrα-(methylsulfinyl)benzyl bromide, /?αrα-(methylsulfinyl)benzyl chloride, 2-picolyl bromide, 2-picolyl chloride, 4-picolyl bromide, 4-picolyl chloride, 3-methyl-2-picolyl N-oxido bromide, 3-methyl-2-picolyl N- oxido chloride, 2-quinolinylmethyl bromide, 2-quinolinylmethyl chloride, 1-pyrenylmethyl bromide, 1 -pyrenylmethyl chloride diphenylmethyl bromide, diphenylmethyl chloride, para, »αrα'-dinitrobenzhydryl bromide, para, para' -dinitrόbenzhydτyl chloride, 5-dibenzosuberyl bromide, 5-dibenzosuberyl chloride, triphenylmethyl bromide, triphenylmethyl chloride, α-naphthyldiphenylmethyl bromide, α-naphthyldiphenylmethyl chloride, pαra-methoxyphenyldiphenylmethyl bromide, > rα-methoxyphenyldiphenylmethyl chloride, di(pαrα-methoxyphenyl)phenylmethyl bromide, di(pαra-methoxyphenyl)phenylmethyl chloride, tri( ara-methoxyphenyl)methyl bromide, tri(pαrα-methoxyphenyl)methyl chloride, 4-(4'-bromophenacyloxy)phenyldiphenylmethyl bromide, 4-(4'-bromophenacyloxy)phenyldiphenylmethyl chloride, 4,4',4"-tris(4, 5- dichlorophthalimidophenyl)methyl bromide, 4,4',4"-tris(4,5-dichlorophthalimidophenyl)- methyl chloride, 4,4',4"-tris(levulinoyloxyphenyl)methyl bromide, 4,4',4"-tris(levulinoyl- oxyphenylmethyl chloride, 4,4',4"-tris(benzoyloxyphenyl)methyl bromide, 4,4',4"-tris(benzoyloxyphenyl)methyl chloride, 4,4'-dimethoxy-3 "-(N-(imidazolyl- methyl))trityl bromide, 4,4'-dimethoxy-3"-(N-(imidazolylmethyl))trityl chloride, 4,4'-dimethoxy-3"-(N-(imidazolylethyl)carbamoyl)trityl bromide, 4,4'-dimethoxy-3"-(/V- (imidazolylethyl)carbamoyl)trityl chloride, l,l-bis(4-methoxyphenyl)- -pyrenylmethyl bromide, l,l-bis(4-methoxyphenyl)- -pyrenylmethyl chloride, 9-anthryl bromide, 9-anthryl chloride, 9-(9-phenyl)xanthenyl bromide, 9-(9-phenyl)xanthenyl chloride, 9-(9-phenyl-10-oxo)anthryl bromide, 9-(9-phenyl-10-oxo)anthryl chloride, l,3-benzodithiolan-2-yl bromide, l,3-benzodithiolan-2-yl chloride, benzisothiazolyl 5,5- dioxido bromide, benzisothiazolyl 5,5-dioxido chloride, trimethylsilyl bromide, trimethylsilyl chloride, triethylsilyl bromide, triethylsilyl chloride, triisopropylsilyl bromide, triisopropylsilyl chloride, dimethylisopropylsilyl bromide, dimethylisopropylsilyl chloride, diethylisopropylsilyl bromide, diethylisopropylsilyl chloride, dimethylthexylsilyl bromide, dimethylthexylsilyl chloride, tert-butyldimethylsilyl bromide, tert-butyldimethylsilyl chloride, tert-butyldiphenylsilyl bromide, tert-butyldiphenylsilyl chloride, tribenzylsilyl bromide, tribenzylsilyl chloride, tri- ? ra-xylylsilyl bromide, tri-pαra-xylylsilyl chloride, triphenylsilyl bromide, triphenylsilyl chloride, diphenylmethylsilyl bromide, diphenylmethylsilyl chloride, di-tert-butylmethylsilyl bromide, di-tert-butylmethylsilyl chloride, tris(trimethylsilyl)silyl, tris(trimethylsilyl)silyl, (2-hydroxystyryl)dimethylsilyl bromide,
(2-hydroxystyryl)dimethylsilyl chloride, (2-hydroxystyryl)diisopropylsilyl bromide, (2-hydroxystyryl)diisopropylsilyl chloride, tert-butylmethoxyphenylsilyl bromide, tert-butylmethoxyphenylsilyl chloride, tert-butoxydiphenylsilyl bromide, tert-butoxydiphenylsilyl chloride, and the like.
Prefeπed selectively removable hydroxy protecting group precursors for the practice of step (g) include benzyl chloride, benzyl bromide, diphenylmethyl chloride, diphenylmethyl bromide, αrα-methoxybenzyl chloride, /?αrα-methoxybenzyl bromide, 3,4-dimethoxybenzyl chloride, 3,4-dimethoxybenzyl bromide, ørtAonitrobenzyl chloride, ørtΛø-nitrobenzyl bromide, /jαrα-nitrobenzyl chloride, /?αra-nitrobenzyl bromide, 2,6-dichlorobenzyl chloride, 2,6-dichlorobenzyl bromide, 2,6-difluorobenzyl chloride, 2,6-difluorobenzyl bromide, 2-trifluoromethylbenzyl chloride, 2-trifluoromethylbenzyl bromide, /rara-cyanobenzyl chloride, /?αra-cyanobenzyl bromide, αrα-acylaminobenzyl chloride, />αrα-acylaminobenzyl bromide, αra-phenylbenzyl chloride, αra-phenylbenzyl bromide, pαra-azidobenzyl chloride, and/?αrα-azidobenzyl bromide, and benzyltrichloroacetimidate.
More prefeπed selectively removable hydroxy protecting group precursors for the practice of step (g) are benzyl chloride or benzyl bromide.
Examples of alkylating agents useful for the practice of step (h) are alkyl halides such as methyl chloride, methyl bromide, methyl iodide, ethyl chloride, ethyl bromide, ethyl iodide, z'sø-propyl chloride, wo-propyl bromide, tsø-propyl iodide, and the like; alkyl trifluoromethanesulfonates such as methyl trifluoromethanesulfonate, ethyl trifluoromethanesulfonate, wø-propyl trifluoromethanesulfonate, and the like; dialkylsulfates such as dimethylsulfate, diethylsulfate, diisopropylsulfate, and the like; cycloalkyalkyl halides such as (chloromethyl)cyclopropane, (bromoethyl)cyclobutane, (iodopropyl)cyclopentane, and the like; (trifluoromethanesulfonylmethyl)cyclopropane, (trifluoromethanesulfonylethyl)cyclobutane, (trifluoromethanesulfonylpropyl)- cyclopentane, and the like; dicycloalkyalkyl sulfates such as di(cyclopropylmethyl)sulfate, di(cyclobutylethyl)sulfate, di(cyclopentylpropyl)sulfate, and the like; aryl-(C2-C4-alkyl) halides such as phenethylbromide, phenpropyl iodide, and the like; aryl-(C2-C4-alkyl) triflates such as trifluoromethyl 2-phenylethoxysulfone, trifluoromethyl 2- phenylpropoxysulfone, and the like; and di-(aryl-(C2-C4-alkyl)) sulfates such as di(phenethyl)sulfate, and the like.
A preferred alkylating agent for the practice of step (h) is methyl iodide. Steps (g) and (h) are conducted at a temperature between about -10 °C and about 30 °C in a solvent such as diethyl ether, tetrahydrofuran, dioxane, 1 ,2-dimethoxyethane, NN-dimethylformamide, toluene, dimethylsulfoxide, acetonitrile, or a mixture thereof. In a prefeπed embodiment, steps (g) and (h) are conducted at about 0 °C in tetrahydrofuran.
Examples of hydroxy protecting group removal agents useful for the practice of step (i) are hydrogen gas and a hydrogenolysis catalyst such as palladium metal, palladium metal on carbon, palladium metal on neutral alumina, palladium metal on acidic alumina, palladium metal on basic alumina, palladium(II) acetate, palladium(II) chloride, palladium(H) hydroxide on carbon, and the like. A preferred hydrogenolysis catalyst for the practice of step (i) is palladium(II) hydroxide on carbon.
Step (i) is conducted at a temperature of between about 0 °C and about 30 °C, at a pressure of about 10 pounds per square inch to about 80 pounds per square inch, in a solvent such as acetone, diethyl ether, dioxane, methanol, ethanol, wø-propanol, tert-butanol, ethyl acetate, iso-propy\ acetate, methylethyl ketone, tetrahydrofuran, or a mixture thereof.
In a preferred embodiment, step (i) is conducted at about 25 °C, at a pressure of about 40 pounds per square inch, in essentially tetrahydrofuran.
In another prefeπed second embodiment, step (j) is conducted, and the product of step (i) is isolated by distillation.
In a third embodiment of this invention is disclosed a process for making the compound having structural formula (12-b)
Figure imgf000013_0001
(12-b), having the stereochemistry illustrated therein, in which
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; and R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl, comprising the steps of: (k) reacting a compound having structural formula (8)
Figure imgf000013_0002
(8), a prefeπed embodiment of which is
2-pentanone, bromoform, potassium hydroxide, and methanol, at a temperature of between about 50 °C and about 70 °C, to provide a compound having structural formula (9)
Figure imgf000014_0001
(9), a prefeπed embodiment of which is
(±)-2-methoxy-2-methylpentanoic acid,
(1) reacting the product of step (k), a second esterifying agent and, optionally, an esterification promotion agent to structural formula (10)
Figure imgf000014_0002
(10), in which R is alkyl, C2-C4-haloalkyl, cycloalkylalkyl, or arylalkyl, a preferred embodiment of which is substantially pure
(±)-methyl 2-methoxy-2-methylpentanoate;
(m) reacting the compound having structural formula (10) and an esterase to provide either an enantiomerically enriched compound having the stereochemistry illustrated by a compound having structural formula (1 1 -a)
Figure imgf000014_0003
(11-a), a prefeπed embodiment of which is substantially pure, enantiomerically enriched (25)-2-methoxy-2-methylpentanoic acid, or an enantiomerically enriched compound having the stereochemistry illustrated by a compound having structural formula (11 -b)
Figure imgf000014_0004
(11-b), a prefeπed embodiment of which is substantially pure, enantiomerically enriched (25)- methyl 2-methoxy-2-methylpentanoate;
(n) reacting either the compound having structural formula (11 -a) or the compound having structural formula (11-b) and a third reducing agent to provide the compound having structural formula (12-b), a prefeπed embodiment of which is substantially pure, enantiomerically enriched
(25)-2-methoxy-2-methyl- 1 -pentanol;
and (o) optionally isolating the compound having structural formula (12-b).
In a prefeπed third embodiment, steps (m) and (n) are conducted continuously, and step (o) is omitted.
In a prefeπed embodiment, step (k) is conducted at about 60 °C.
Examples of second esterifying agents useful for the practice of step (1) include z'sø-butylene, a -C alcohol such as methanol, ethanol, and ώø-propanol, tert-butyoxycarbonyl-2-(l-acetamido-2-methoxy-2-methyl)pentyl-3-(cis-propeny-l- yl)pyrrolidine-5-carboxylic acid tert-butyl ester, and the like, and, optionally an acid such as hydrochloric acid or sulfuric acid. Alternatively, the alcohol can be reacted with an esterification promotion agent such as methyl chloroformate, ethyl chloroformate, z'sø-butyl chloroformate, and the like, and a base such as N-methylmorpholine and the like, to provide a mixed anhydride intermediate which, when reacted with an alcohol such as methanol, ethanol, or trifluoroethanol, provides a compound having structural formula (10).
A prefeπed second esterifying agent for the practice of step (1) is methanol and sulfuric acid.
Examples of esterases useful for the practice of step (m) are Amano PS 30 Lipase, Atnano AY Candida Cylindracea, Aspergillus niger lipase, Aspergillus oryza protease, Alcaligenes species lipase, Aspergillus species protease, Bacillus species protease, Candida antartica "A" lipase, Candida antartica "B" lipase, Candida lipolytica lipase, Candida Rugosa esterase, Candida Rugosa lipase, ChiroCLEC-CR, ChiroCLEC-BL, ChiroCLEC-PC, ChiroCLEC-EC, alpha-crymotrypsin, Humicola lanuginosa lipase, Mucor melhel lipase, Papain, PeptiCLEC-TR, Penicillin acylase, Pig Liver enzyme, Porcine Liver esterase, Porcine Pancreatic lipase, Pseudomonas cepacia lipase, Rhizopus Arrhizus Lipase Type XI, Rhizopus delmar lipase, and the like. indent Prefeπed esterases for the practice of step (1) are Candida Rugosa lipase, Pig Liver enzyme, Amano PS 30 Lipas, Amano AY Candida Cylindracea, Porcine Pancreatic lipase, and Rhizopus Arrhizus Lipase Type XI. A more preferred esterase for the practice of step (m) is Candida Rugosa Lipase. In another embodiment for the practice of step (m), the esterase concentration is between about 20 mg per mL and about 40 mg per mL. In a prefeπed embodiment for the practice of this step, the esterase concentration is about 36 mg per mL. In still another embodiment for the practice of step (m), the pH of the solution is between about 5.5 and about 8.5. In a more prefeπed embodiment for the practice of this step, the pH is about 8.
Step (m) is conducted at a temperature of between about 20 °C and about 50 °C in a solvent such as acetone, acetonitrile, a Cj-Cs alcohol such as methanol, ethanol, and ώø-propanol, dimethylsulfoxide, dioxane, heptane, hexane, methylethyl ketone, tetrahydrofuran, toluene, water, or a mixture thereof.
In a prefeπed embodiment, step (m) is conducted at a temperature of about 37 °C in essentially a mixture of water and acetone.
Examples of third reducing agents useful for the practice of step (n) are borane dimethylsulfide, borane-THF, sodium borohydride and iodine, aluminum hydride, aluminum hydride triethylamine, di(κO-butyl)aluminum hydride, zso-propoxyaluminum hydride, tert-butoxyaluminum hydride, di(tert-butoxy)aluminum hydride, lithium aluminum hydride, lithium aluminum hydride-N-methylpyrrolidine, sodium aluminum hydride, sodium diethylaluminum hydride, bis(2-methoxyethoxy)aluminum hydride, and lithium di(z',so-butyl)(butyl)aluminum hydride.
The choice of third reducing agents for the practice of step (n) depends on the intermediate. An intermediate having structural formula (11-a) will be more efficiently reduced with a borane agent while an intermediate having formula (11 -b) will be more efficiently reduced with an aluminum hydride agent. In a prefeπed embodiment for the practice of step (m), the product of step (m) is a compound having formula (1 1-a), and the third reducing agent is borane dimethylsulfide.
Step (n) is conducted at a temperature between about 0 °C and about 50 °C in a solvent such as acetone, acetonitrile, a -C5 alcohol such as methanol, ethanol, and fso-propanol, dichloromethane, dimethyl sulfide, dimethylsulfoxide, diethyl ether, dioxane, heptane, hexane, methylethyl ketone, tetrahydrofuran, toluene, water, or a mixture thereof.
In a prefeπed embodiment, step (n) is conducted in essentially a mixture of dichloromethane and dimethyl sulfide at a temperature of about 25 °C.
The compound having structural formula (12) is useful as an intermediate for making a compound having structural formula (15)
Figure imgf000017_0001
(15), in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2 .
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl);
L1 is N(R7), O, S, S(O), or SO2;
R is aryl, furanyl, or, thienyl in which the aryl, the furanyl, and the thienyl are unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and η
R is hydrogen, alkyl, aryl, or ?αrα-toluenesulfonyl. In fourth embodiment of this invention, therefore, is disclosed a process for making a compound having structural formula (15) from the compound having structural formula (12) comprising, in toto, the steps of: (p) reacting the compound having structural formula (12)
Figure imgf000017_0002
(12), the prefeπed embodiment of which is the compound having the stereochemistry illustrated by the compound having structural formula (1 -a)
Figure imgf000017_0003
(12-a), the more preferred embodiment of which is the compound having the stereochemistry illustrated by the compound having structural formula (12-b)
Figure imgf000017_0004
(12-b), and the still more prefeπed embodiment of which is substantially pure, enantiomerically enriched
(25)-2-methoxy-2 -methyl- 1 -pentanol, an oxidant, a second base, and, optionally, a first additive, in which the oxidant, the second base, and the additive are substantially soluble in the solvent or solvents in which this step is conducted, to structural formula (13)
Figure imgf000018_0001
(13), a prefeπed embodiment of which is a compound having the stereochemistry illustrated by a compound having structural formula (13-a)
Figure imgf000018_0002
(13-a), and a more prefeπed embodiment of which is substantially pure, enantiomerically enriched
(25)-2-methoxy-2-methylpentanal;
and
(q) reacting the product of step (p), a compound having structural formula (14)
, 1 H2N" "C(R6)3
(14), a prefeπed embodiment of which is substantially pure triphenylmethanesulfenamide, a drying agent, and, optionally, a first acid catalyst to provide the compound having structural formula (15), a prefeπed embodiment of which is a compound having the stereochemistry illustrated by a compound having
Figure imgf000018_0003
(15-a), and a more prefeπed embodiment of which is substantially pure, enantiomerically enriched
( lE,25)-2-methoxy-2-methylpentanal 5-tritylthioxime. In a prefeπed fourth embodiment, steps (p) and (q) are conducted in situ. Examples of oxidants useful for the practice of step (p) are an activated dimethyl sulfoxide agent such as dimethylsulfoxide and oxalyl chloride, dimethylsulfoxide- SO3 pyridine, tetrapropylammonium perruthenate, 2,2,6,6-tetramethyl- 1 -piperidinyloxy, and the like. Examples of first additives useful for the practice of step (p) are sodium hypochlorite/sodium bromide, potassium hypochlorite/potassium bromide, sodium hypochlorite/potassium bromide, potassium hypochlorite/sodium bromide, /V-methylmorpholine-/V-oxide, and the like.
In a prefeπed embodiment for the practice of step (p), the oxidant is an activated dimethyl sulfoxide agent, and the first additive is omitted. In a particularly prefeπed embodiment for the practice of this step, the oxidant is dimethylsulfoxide Sθ3 pyridine.
Examples of second bases useful for the practice of step (p) are diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, l,8-diazobicyclo[5.4.0]undec-7-ene, l,5-diazobicyclo[4.3.0]non-5-ene, 1-methylpiperidine, pyrazine, pyridazine, pyrimidme, pyridine, tetramethylenediamino- methane, tributylamine, triethylamine, and tripropylamine.
In a prefeπed embodiment for the practice of step (p), the second base is triethylamine.
Step (p) is conducted at a temperature between about -10 °C and about 30 °C in a solvent such as chloroform, dichloromethane, diethyl ether, dioxane, ethyl acetate, dimethylsulfoxide, N/V-dimethylformamide, wø-propyl acetate, tetrahydrofuran, toluene, or a mixture thereof.
In a prefeπed embodiment, step (p) is conducted in essentially dichloromethane and dimethylsulfoxide at a temperature of about 0 °C, after which the dimethylsulfoxide is substantially removed to provide the product of step (p) as a solution comprising between about 20% and about 40% by weight of the compound having structural formula (13) in dichloromethane. In a more preferred embodiment of this step, the product is a solution comprising about 30% by weight of the compound having structural formula (13) in dichloromethane . Examples of drying agents useful for the practice of step (q) are 3 A sieves, 4A sieves, anhydrous sodium sulfate, anhydrous magnesium sulfate, anhydrous potassium carbonate, and the like.
A prefeπed drying agent for the practice of step (q) is anhydrous sodium sulfate. Examples of first acid catalysts for the practice of step (q) are camphorsulfonic acid, acetic acid/sodium acetate, pyridiniumjcαra-toluene sulfonate, and jαra-toluenesulfonic acid. A prefeπed first acid catalyst for the practice of step (q) is pyridinium /?αrα-toluene sulfonate.
Step (q) is conducted at a temperature between about 0 °C and about 30 °C in a solvent such as chloroform, dichloromethane, diethyl ether, dimethylsulfoxide, dioxane, NN-dimethylformamide, ethyl acetate, wø-propyl acetate, tetrahydrofuran, toluene, ørtλø-xylene, weto-xylene, αr -xylene, tetrahydrofuran, or a mixture thereof.
In a prefeπed embodiment, step (q) is conducted at about 25 °C in essentially dichloromethane, after which the dichloromethane is substantially replaced with heptane to provide between about 40% and about 70% by weight of the compound having structural formula (15) in heptane. In a more prefeπed embodiment of this step, the product is a solution comprising essentially about 50% by weight of the compound having structural formula (15) in heptane.
In a fifth embodiment of this invention is disclosed a process for making substantially pure (±)-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate comprising, in toto, the steps of:
(r) reacting (±)-4-amino-3-hydroxy-«-butyric acid, a silating agent, and a third base to provide (±)-4-trimethylsilyloxy-2-oxo-pyπolidine;
(s) reacting the (±)-4-trimethylsilyloxy-2-oxo-pyπolidine and a tert-butylcarbonyloxy- introducing agent, the third base, and 4-dimethylaminopyridineto provide (±)-tert-butyl-4-trimethylsilyloxy-2-oxo-pyπolidinecarboxylate;
(t) reacting the (±)-tert-butyl-4-trimethylsilyloxy-2-oxo-pyπolidinecarboxylate and a desilylating agent to provide (-fc)-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate;
and
(u) isolating the substantially pure (±)-tert-butyl-4-hydroxy-2-oxo-pynolidine- carboxylate.
In a prefeπed fifth embodiment, steps (r), (s), (t), and (u) are conducted sequentially.
Examples of silating agents useful for the practice of step (r) are 1,1,1,3,3,3- o hexamethyldisilazane, a compound of formula Si(R )3(C1) in which each R is independently selected from the group consisting of alkyl and unsubstituted aryl, N,O-bis(trimethylsilyl)acetamide, and the like. A prefeπed silating agent for the practice of step (r) is (±)-l, 1,1 ,3,3,3- hexamethyldisilazane, which preferably is present between about 1 molar equivalent and about 2 molar equivalents per molar equivalent of the (±)-4-amino-3-hydroxy-«-butyric acid. In a more preferred embodiment of this step, the 1,1,1,3,3,3-hexamethyldisilazane is present in about 1.61 molar equivalents per molar equivalent of the (±)-4-amino-3- hydroxy-«-butyric acid.
Examples of third bases useful or the practice of step (r) are diethylenediamine, diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, l,8-diazobicyclo[5.4.0]undec-7-ene, l,5-diazobicyclo[4.3.0]non-5-ene, 1-methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediammo- methane, tributylamine, triethylamine, and tripropylamine.
A prefeπed third base for the practice of step (r) is pyridine, which preferably is present between about 0.01 to about 10 molar equivalents per molar equivalent of the (±)-4-amino-3-hydroxy-«-butyric acid. In a more prefeπed embodiment of this step, the pyridine is present in about 7.4 molar equivalents per molar equivalent of the (±)-4-amino- 3-hydroxy-H-butyric acid.
Step (r) is conducted at a temperature between about 100 °C and about 150 °C in a solvent such as toluene, ørtΛø-xylene, wetα-xylene, /?αrα-xylene, or a mixture thereof. In a prefeπed embodiment, step (r) is conducted at about 130 °C to about 140 °C in essentially a mixture comprising ørtλø-xylene, meta-xylene, and /jαr -xylene, after which the solvent is substantially removed.
Examples of tert-butylcarbonyloxy-introducing agents useful for the practice of step (s) are di-tert-butyl dicarbonate, l-(tert-butoxycarbonyl)-2-tert-butyl-3-methyl-4- imidazolidinone, (2-tert-butoxycarbonyloxyimino)-2-phenylacetonitrile), and the like.
A preferred tert-butylcarbonyloxy-introducing agent for the practice of step (s) is di-tert-butyl dicarbonate, which preferably is present in about 0.9 to about 1.5 molar equivalents per molar equivalent of the (±)-tert-butyl-4-hydroxy-2-oxo- pyπolidinecarboxylate. In a more prefeπed embodiment of this step, the di-tert-butyl dicarbonate is present in about 1.2 molar equivalents per molar equivalent of the (±)-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate.
In another prefeπed embodiment, the 4-dimethylaminopyridine in step (s) is present in about 0.01 to about 0.1 molar equivalents per molar equivalent of the (±)-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate. In a more preferred embodiment of this step, the 4-dimethylaminopyridine is present in about 0.05 molar equivalents per molar equivalent of the (±)-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate.
Step (s) is conducted at a temperature between about -10 °C and about 30 °C in a solvent such as dioxane, ethyl acetate, z'so-propyl acetate, tetrahydrofuran, or a mixture thereof.
In a prefeπed embodiment, step (s) is conducted at about 0 °C to about 25 °C in tetrahydrofuran, zsø-propyl acetate, or a mixture thereof. In a more prefeπed embodiment, step (s) is conducted at about 0 °C to about 25 °C in tetrahydrofuran.
In another more prefeπed embodiment, step (s) is conducted at about 0 °C to about 25 °C in fso-propyl acetate. Examples of desilylating agents useful for the practice of step (t) are 2,3-dichloro-
5,6-dicyano-l,4-benzoquinone in ethyl acetate and water, polymer-bound ammonium fluoride, tetrabutylammonium fluoride, triethylamine trihydrofluoride, pyridine-HF, potassium carbonate in anhydrous methanol, and the like.
A preferred desilylating agent for the practice of step (t) is triethylamine-trihydrofluoride.
Step (t) is conducted at a temperature between about -10 °C and about 30 °C in a solvent such as dioxane, ethyl acetate, z'sø-propyl acetate, tetrahydrofuran, or a mixture thereof.
In a preferred embodiment, step (t) is conducted at about 0 °C to about 25 °C in tetrahydrofuran, tsø-propyl acetate, or a mixture thereof.
In a more preferred embodiment, step (t) is conducted at about 0 °C to about 25 °C in tetrahydrofuran.
In another more prefeπed embodiment, step (t) is conducted at about 0 °C to about 25 °C in wø-propyl acetate. In another preferred fifth embodiment, the practice of step (u) comprises isolation of the substantially pure (±)-tert-butyl-4-hydroxy-2-oxo-pyπolidinecarboxylate by precipitation of the same from either essentially tetrahydrofuran or essentially zsø-propyl acetate.
In still another prefeπed fifth embodiment, the practice of step (u) further comprises isolation of additional substantially pure (±)-tert-butyl-4-hydroxy-2-oxo- pyπolidinecarboxylate by treatment of the tetrahydrofuran or the zsø-propyl acetate with heptane and cooling the resulting solution to a temperature of about 0 °C to precipitate the additional substantially pure (±)-tert-butyl-4-hydroxy-2-oxo-pyrrolidine.
The compound having structural formula (15-a) and the (±)-tert-butyl-4-hydroxy- 2-oxo-pyπolidinecarboxylate are useful intermediates for making a compound having structural formula (19-a)
Figure imgf000022_0001
(19-a), in which the absolute stereochemistry is illustrated therein, and in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2 .
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
4 . R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl); L1 is N(R7), O, S, S(O), or SO2;
R is aryl, furanyl, or thienyl, in which the aryl, the furanyl, and the thienyl are unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and η R is hydrogen, alkyl, aryl, or αrα-toluenesulfonyl.
In a sixth embodiment of this invention, therefore, is disclosed a process for making a compound having structural formula (19-a) from the compound having structural formula (15-a) and the (±)-tert-butyl-4-hydroxy-2-oxo-pyπolidine-carboxylate comprising, in toto, the steps of: (v) reacting the (±)-tert-butyl-4-hydroxy-2-oxo-pyπolidinecarboxylate, a fourth base, and a compound having structural formula (16)
X -SO2-R
(16) g in which R is alkyl, haloalkyl, and aryl, in which the aryl is unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and X1 is Br, Cl, or OSO -R9, a prefeπed embodiment of which is methanesulfonyl chloride, to provide tert-butyl 2-oxo-3-pyrroline carboxylate;
(w) reacting the tert-butyl 2-oxo-3-pyπoline carboxylate, a fifth base, and a compound having structural formula (17)
(R8)3SiOSO2CF3 (17), in which each R is independently selected from the group consisting of alkyl and unsubstituted aryl, a prefeπed embodiment of which is tert-butyldimethylsilyl trifluoromethanesulfonate, to provide a compound having structural formula (18)
Figure imgf000024_0001
(18), a prefeπed embodiment of which is tert-butyl 2-((tert-butyl(dimethyl)silyl)oxy)- 1 H-pyπole- 1 -carboxylate;
(x) reacting the product of step (w), a second acid, and a substantially enantiomerically enriched compound having the structural formula (15-a)
Figure imgf000024_0002
(15-a), a prefeπed embodiment of which is substantially pure, substantially enantiomerically enriched
(lE,25)-2-methoxy-2-methylpentanal 5-tritylthioxime, to provide a mixture comprising two diastereomeric forms of a compound having formula (19)
Figure imgf000024_0003
(19), one of which is the compound having the absolute stereochemistry illustrated by a compound having structural formula (19-a)
Figure imgf000024_0004
(19-a), in which the substituents at the carbons labeled "1" and "2" are erythro relative to each other and "and-" relative to the O-R group at the carbon labeled "3," a prefeπed embodiment of which is substantially pure, diastereomerically enriched tert-butyl (2R)-2-((li?,25)-2-methoxy-2-methyl-l-((tritylsulfanyl)amino)pentyl)-5-oxo- 2,5-dihydro-l - 1 H-pyπole- 1 -carboxylate, and the other of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (19-b)
Figure imgf000025_0001
(19-b), in which the substituents at the carbons labeled "1" and "2" are also erythro relative to each other but are "syn-" relative to the O-R group at the carbon labeled "3," a prefeπed embodiment of which is tert-butyl (25)-2-(( 15,25)-2-methoxy-2-methyl- 1 -
((tritylsulfanyl)amino)pentyl)-5-oxo-2,5-dihydro- 1-1 H-pyrrole-1 -carboxylate, in which the (19-a)/(19-b) ratio in the mixture is about 4.3: 1 to about 10: 1;
(y) allowing the mixture of the compound having structural formula (19-a) and the compound having structural formula (19-b) to further equilibrate until the (19-a)/(19-b) ratio in the mixture is greater than 10: 1 ;
and
(z) isolating the diastereomerically enriched compound having structural formula (19-a). In a prefeπed sixth embodiment, steps (v) and (w) are conducted in situ, steps
(x) and (y) are conducted sequentially, and steps (y) and (z) are conducted in situ.
Examples of fourth bases usefiil for the practice of step (v) are diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, 1 ,8-diazobicyclo[5.4.0]undec-7-ene, 1 ,5-diazobicyclo[4.3.0]non-5-ene, 1 -methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediamino- methane, tributylamine, triethylamine, tripropylamine, and the like.
A prefeπed fourth base for the practice of step (v) is triethylamine.
Step (v) is conducted at a temperature between about -10 °C and about 20 °C in a solvent such as carbon tetrachloride, chloroform, dichloromethane, dioxane, tetrahydrofuran, or a mixture thereof.
In a prefeπed embodiment, step (v) is conducted at about 0 °C in essentially tetrahydrofuran, after which the tetrahydrofuran is substantially replaced with heptane.
Examples of fifth bases useful for the practice of step (w) are diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, l,8-diazobicyclo[5.4.0]undec-7-ene, l,5-diazobicyclo[4.3.0]non-5-ene, 1-methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediamino- methane, tributylamine, triethylamine, and tripropylamine, and the like. A prefeπed fourth base for the practice of step (w) is triethylamine.
Step (w) is conducted at a temperature between about -10 °C and about 20 °C in a solvent such as carbon tetrachloride, chloroform, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
In a prefeπed embodiment, step (w) is conducted at about 0 °C in essentially heptane and dichloromethane, after which the dichloromethane is substantially removed.
Examples of second acids useful for the practice of step (x) are boron trifluoride diethyletherate, copper(II) bis(trifluoromethanesulfonate), trifluoromethanesulfonic acid, titanium r'sø-propoxide, titanium tetrachloride, trimethylsilyltrifluoromethane sulfonate, tributylsilyltrifluoromethane sulfonate, ytterbium tetrakis(trifluoromethanesulfonate), zinc chloride, and the like.
A prefeπed second acid for the practice of step (x) is trifluoromethanesulfonic acid.
Step (x) is conducted at a temperature between about -50 °C and about -30 °C in a solvent such as acetonitrile, chloroform, carbon tetrachloride, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
In a preferred embodiment, step (x) is conducted at about -40 °C in essentially heptane and tetrahydrofuran.
Step (y) is conducted at a temperature between about -50 °C and about -30 °C in a solvent such as acetonitrile, chloroform, carbon tetrachloride, dichloromethane, dioxane, heptane, hexane, tetrahydrofuran, or a mixture thereof.
In a preferred embodiment, step (y) is conducted at about -40 °C in essentially heptane and tetrahydrofuran.
In a prefeπed embodiment of step (z), the tetrahydrofuran is substantially replaced with heptane to precipitate a substantially pure compound having structural formula (19-a), which is then isolated with a diastereomeric excess greater than about 90: 1. In a more prefeπed embodiment of this step, the compound having structural formula (19-a) is isolated with a diastereomeric excess greater than about 99: 1.
A compound having structural formula (19) is useful as an intermediate for making a compound having structural formula (24)
Figure imgf000027_0001
(24) in which the carbon-carbon double bond is substantially in the Z configuration, and in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2 R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
4 R is alkyl, cycloalkyalkyl, or aryl-(C2-C -alkyl); and
R is methyl, ethyl, ώø-propyl, or vinyl.
In a seventh embodiment of this invention, therefore, is disclosed a process for making a compound having structural formula (24) from the compound having structural formula (19) comprising, in toto, the steps of:
(aa) reacting a compound having structural formula (19)
Figure imgf000027_0002
(19), a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a c -a)
Figure imgf000027_0003
(19-a), and a more preferred embodiment of which is substantially pure, diastereomerically enriched tert-butyl (2R)-2-((lR,25)-2-methoxy-2-methyl-l-((tritylsulfanyl)amino)pentyl)-5-oxo-2,
5-dihydro- 1 - 1 H-pyπole- 1 -carboxylate, a conjugate addition agent, said conjugate addition agent comprising a mixture of compounds having structural formula (20-Z)
Figure imgf000028_0001
(20-Z) and structural formula (20-E)
Figure imgf000028_0002
(20-E), in which the (20-Z)/(20-E) ratio in the mixture is about 97:3, and in which Q is Li, Mg-Cl, Mg-Br, or Mg-I, and, optionally, a second additive at a temperature between about -50 °C and about -30 °C about to provide a compound having structural formula (21)
Figure imgf000028_0003
(21), a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (21-a)
Figure imgf000028_0004
(21-a), and a more prefeπed embodiment of which is substantially pure, diastereomerically enriched tert-butyl (2R,3S)-2-(( lR,25)-2-methoxy-2-methyl- 1 -((tritylsulfanyl)amino)pentyl)-5-oxo- 3 -(( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate;
(bb) reacting the product of step (aa) and a third acid to provide a compound having the structural formula (22)
Figure imgf000029_0001
or a salt thereof, a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (22-a)
Figure imgf000029_0002
(22-a), and a more prefeπed embodiment of which is substantially pure, diastereomerically enriched (4S,5R)-5-((lR,2S)- 1 -amino-2-methoxy-2-methylpentyl)-4-(( 1 Z)- 1 -propenyl)-2- pyπolidinone;
(cc) reacting the product of step (bb), an acetylating agent, and a sixth base to provide a compound having the structural formula (23)
Figure imgf000029_0003
a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (23 -a)
Figure imgf000030_0001
(23-a), and a more prefeπed embodiment of which is substantially pure, diastereomerically enriched N-((lR,25)-2-methoxy-2-methyl-l-((2R,35)-5-oxo-3-((lZ)-l- propenyl)pyπolidinyl)pentyl)acetamide;
(dd) reacting the product of step (cc), a tert-butylcarbonyloxy-introducing agent, a seventh base, and 4-dimethylaminopyridine to provide the compound having formula (24), a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (24-a)
Figure imgf000030_0002
(24-a), and a more prefeπed embodiment of which is substantially pure, diastereomerically enriched tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-oxo-3-((lZ)-
1 -propenyl)- 1 -pyπolidinecarboxylate;
and
(ee) optionally isolating the product of step (dd).
In a prefeπed seventh embodiment, steps (aa), (bb), (cc), (dd), and (ee) are conducted in situ.
Examples of second additives useful for the practice of step (aa) are compounds
8 8 having formula Si(R )3(C1), in which each R is independently alkyl or unsubstituted aryl, g compounds having formula Si(R )3(Br), and the like.
In a preferred embodiment for the practice of step (aa) the second additive is employed, is trimethylsilyl chloride, and is present in about 0.5 to about 4 molar equivalents per molar equivalent of the compound having structural formula (19). In a more preferred embodiment of this step, the second additive is present in about 3 molar equivalents per molar equivalent of the compound having structural formula (19).
In a prefeπed embodiment, step (aa) is conducted at about -25 °C in a solvent such as acetonitrile, chloroform, dichloromethane, ethyl acetate, z'sø-propyl acetate, tetrahydrofuran, toluene, or a mixture thereof. In a more prefeπed embodiment, step (aa) is conducted at about -25 °C in essentially tetrahydrofuran and toluene.
In another part of the seventh embodiment of this invention, the conjugate addition agent used for the practice of step (aa) is made by reacting a mixture, said mixture comprising a precursor compound having structural formula (20-2?)
Figure imgf000031_0001
(20-2?) and a precursor compound having structural formula (20-£p)
Q1^^RIO
(20-^), in which the (20-2?)/(20-Ep) ratio in the mixture is about 97:3, and in which Q is Li, Mg-Cl, Mg-Br, or Mg-I, a cuprous adjuvant, and optionally, a ligand selected from the group comprising tri-n-butylphosphine, tri-wø-butylphosphine, and tri-n-pentylphosphine.
Examples of the cuprous adjuvant useful for the practice of step (aa) are copper(I) bromide, copper(I) bromide-dimethyl sulfide, copper(I) chloride, copper(I) bromide, copper(I) iodide, copper(I) cyanide, copper(I) tert-butoxide, copper(I) thiophenoxide, copper(I) thioisocyanate, copper(I) acetylide, copper(I) 3,3-dimethyl-l-butynide, copper(I) 1 -pentynide, and the like.
In a prefeπed embodiment for the practice of step (aa), the ligand is omitted and the cuprous adjuvant is copper(I) bromide-dimethyl sulfide complex, which is present in about 0.05 molar equivalents to about 1.2 molar equivalents per molar equivalent of the compound having structural formula (19). In a more prefeπed embodiment of this step, the cuprous adjuvant is present in about 0.5 molar equivalents per molar equivalent of the compound having structural formula (19). In still another part of the seventh embodiment of this invention, the 97:3 (20-Z)/(20-E) mixture used for the practice of step (aa), is present in about 0.9 molar equivalents to about 3.5 molar equivalents per molar equivalent of the compound having structural formula (19). In a more preferred embodiment of this step, the 97:3 (20-2)/(20-E) mixture is present in about 3 molar equivalents per molar equivalent of the compound having structural formula (19).
Examples of third acids useful for the practice of step (bb) are hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, trifluoroacetic acid, />αrø-toluenesulfonic acid, pyridinium αrø-toluenesulfonic acid, camphorsulfonic acid, and the like.
In a preferred embodiment for the practice of step (bb), the third acid is hydrochloric acid.
Step (bb) is conducted at a temperature between about -10 °C and about -30 °C in a solvent such as ethyl acetate, z'sø-propyl acetate, tetrahydrofuran, toluene, water, or a mixture thereof.
In a preferred embodiment, step (bb) is conducted at a temperature of about -20 °C in essentially tetrahydrofuran, toluene, and water.
Examples of acetylating agents useful for the practice of step (cc) are acetic anhydride, acetyl chloride, acetyl bromide, and the like.
In a prefeπed embodiment for the practice of step (cc), the acetylating agent is acetic anhydride. Examples of sixth bases for the practice of step (cc) are lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, diethylenediamine, diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, 1 ,8-diazobicyclo[5.4.0]undec-7-ene, 1 ,5-diazobicyclo[4.3.0]non- 5-ene, 1-methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediaminomethane, tributylamine, triethylamine, tripropylamine, and the like.
In a preferred embodiment for the practice of step (cc), the sixth base is sodium hydroxide.
Step (cc) is conducted at a temperature between about 0 °C and about 35 °C in a solvent selected from the group comprising chloroform, dichloromethane, tetrahydrofuran, toluene, water, or a mixture thereof.
In a prefeπed embodiment, step (cc) is conducted at about 25 °C in essentially water.
Examples of tert-butylcarbonyloxy-introducing agents useful for the practice of step (dd) are di-tert-butyl dicarbonate, l-(tert-butoxycarbonyl)-2-ter/-butyl-3-methyl-4- imidazolidinone, (2-tert-butoxycarbonyloxyimino)-2-phenylacetonitrile), and the like.
In a prefeπed embodiment for the practice of step (dd), the tert-butylcarbonyloxy- introducing agent is di-tert-butyl dicarbonate.
Examples of seventh bases useful for the practice of step (dd) are diethylmethylamine, diisopropylethylamine, dimethylbutylamine, 1 ,4-dimethylpiperazine, 1 ,8-diazobicyclo[5.4.0]undec-7-ene, 1 ,5-diazobicyclo[4.3.0]non-5-ene, 1 -methylpiperidine, pyrazine, pyridazine, pyrimidine, pyridine, tetramethylenediaminomethane, tributylamine, triethylamine, tripropylamine, and the like.
In a prefeπed embodiment for the practice of step (dd), the seventh base is triethylamine.
Step (dd) is conducted at a temperature between about 0 °C and about 35 °C in a solvent such as acetonitrile, ethyl acetate, wø-propyl acetate, tetrahydrofuran, toluene, water, or a mixture thereof.
In a prefeπed embodiment, step (dd) is conducted at about 25 °C in essentially tetrahydrofuran.
In a prefeπed embodiment of step (ee), the tetrahydrofuran solution is mixed first with z'so-propyl acetate, then with heptane, to crystallize the compound having structural formula (24).
A compound having structural formula (24) is useful as an intermediate for making a compound having structural formula (28)
Figure imgf000033_0001
(28), or a therapeutically acceptable salt thereof, in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyalkyl, or aryl-(C2-C -alkyl); R is methyl, ethyl, zsø-propyl, or vinyl; and
12
R is hydrogen or alkyl.
In an eighth embodiment of this invention, therefore, is disclosed a process for making a compound having structural formula (28) from the compound having structural formula (24) comprising the steps of: (ff) reacting a compound having structural formula (24)
Figure imgf000034_0001
(24), a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (24-a)
Figure imgf000034_0002
(24-a), and a more prefeπed embodiment of which is substantially pure, diastereomerically enriched tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-oxo-3-((12T)-
1 -propenyl)- 1 -pyrrolidinecarboxylate, and a fourth reducing agent to provide a compound having structural formula (25)
Figure imgf000034_0003
(25), a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula (25-a)
Figure imgf000035_0001
(25-a), and a more prefeπed embodiment of which is substantially pure, diastereomerically enriched 2: 1 anomeric tert-butyl (2R,35)-2-((li?,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5- hydroxy-3 -(( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate ;
(gg) optionally reacting the product of step (ff), a -C5 alcohol, a trialkylorthoformate, and a second acid catalyst to formula (26)
Figure imgf000035_0002
in which R , 11 i •s methyl, ethyl, propyl, or z'so-propyl, a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a compound having structural formula
Figure imgf000035_0003
(26-a), and a more preferred embodiment of which is substantially pure, diastereomerically enriched tert-butyl (2R,3S)-2-((lR,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-5-methoxy-3- (( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate; (hh) reacting the product of step (ff) or step (gg), a cyanide-donating agent, and a fourth acid to provide a compound having structural formula 27
Figure imgf000036_0001
(27), a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a
Figure imgf000036_0002
(27-a), and a more preferred embodiment of which is substantially pure, diastereomerically enriched tert-butyl (2R,35,5R)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-cyano-3- (( 1 TJ)- 1 -propenyl)- 1 -pyπolidinecarboxylate;
(ii) reacting the product of step (hh), a -C5 alcohol, and a fifth acid to provide the compound having structural formula (28), a prefeπed embodiment of which is a compound having the absolute stereochemistry illustrated by a
Figure imgf000036_0003
(28-a), and a more prefeπed embodiment of which is substantially pure, diastereomerically enriched isopropyl (2R,5R)-5-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-4-((lZ)-l- propenyl-2 -pyπolidinecarboxylate, or a therapeutically acceptable salt thereof;
and
(jj) isolating the product of step (ii).
In a prefeπed eighth embodiment, step (gg) is conducted, and steps (ff), (gg), (hh), and (ii) are conducted in situ.
Examples of fourth reducing agents useful for the practice of step (ff) are lithium borohydride, sodium borohydride, potassium borohydride, lithium di(z'sø-butyl)aluminum hydride, lithium triethylborohydride, bis(2-methoxyethoxy)aluminum hydride, lithium tri- seobutylborohydride, potassium tri-sec-butylborohydride, lithium aluminum hydride-N- methylpyrrolidine, and the like.
In a prefeπed embodiment for the practice of step (ff), the fourth reducing agent is lithium triethylborohydride.
Step (ff) is conducted at a temperature between about -20 °C and about 25 °C in a solvent such as chloroform, dibutylether, dichloromethane, diethylether, 1 ,2-dimethoxyethane, dioxane, hexane, heptane, tetrahydrofuran, toluene, or a mixture thereof.
In a prefeπed embodiment, step (ff) is conducted at about -15 °C to about 17 °C in essentially tetrahydrofuran.
Examples of -C3 alcohols useful for the practice of step (gg) are methanol, ethanol, propanol, z'so-propanol, and the like.
In a prefeπed embodiment for the practice of step (gg), the -C3 alcohol is methanol.
Examples of trialkylorthoformates useful for the practice of step (gg) are trimethylorthoformate, triethylorthoformate, tripropylorthoformate, triisopropylorthoformate, and the like.
In a prefeπed embodiment for the practice of step (gg), the trialkylorthoformate is trimethylorthoformate .
Examples of second acid catalysts for the practice of step (gg) are pyridinium />αra-toluenesulfonate,/?-zra-toluenesulfonic acid, camphorsulfonic acid, sulfuric acid, methanesulfonic acid, and the like.
In a prefeπed embodiment for the practice of step (gg), the second acid catalyst is camphorsulfonic acid. Step (gg) is conducted at a temperature between about 0 °C and about 30 °C in a solvent such as methanol, ethanol, H-propanol, and ώø-propanol.
In a prefeπed embodiment, step (gg) is conducted at about 25 °C in essentially methanol. Examples of cyanide-donating agents useful for the practice of step (hh) are sodium cyanide, trimethylsilylcyanide, tert-butyldimethylsilyl cyanide, zinc cyanide, diethylaluminum cyanide, and the like.
In a preferred embodiment for the practice of step (hh), the cyanide-donating agent is trimethylsilylcyanide. Examples of fourth acids useful for the practice of step (hh) are aluminum chloride, boron trifluoride-diethyletherate, diethylaluminum chloride, magnesium bromide diethyletherate tin(IV) chloride, titanium(IV) chloride, titanium(IV) tris(chloro)/5ø-propoxide, titanium(IN) bis(chloro)diisopropoxide, trifluoromethanesulfonic acid, tert-butyldimethylsilyl trifluoromethanesulfonate, triisopropylsilyl trifluoromethanesulfonate, trimethylsilyl trifluoromethanesulfonate, and triethylsilyl trifluoromethanesulfonate.
In a prefeπed embodiment for the practice of step (hh), the fourth acid is trifluoromethanesulfonic acid.
Step (hh) is conducted at a temperature between about -50 °C and about 0 °C in a solvent such as acetonitrile, dichloromethane, dibutylether, diethylether, tetrahydrofuran, toluene, or a mixture thereof.
In a preferred embodiment, step (hh) is conducted at about -40 °C in essentially acetonitrile.
Examples of fifth acids useful for the practice of step (ii) are hydrogen chloride/hydrochloric acid, hydrogen bromide/hydrobromic acid, sulfuric acid, trifluoromethanesulfonic acid, and the like.
In a prefeπed embodiment for the practice of step (ii), the fifth acid is hydrogen chloride/hydrochloric acid.
Step (ii) is conducted at a temperature beginning between about -50 °C and about -20 °C and ending between about 80 °C and about 90 °C in methanol, ethanol, propanol, z'sø-propanol, butanol, 1 -methyl- 1-butanol, 2-methyl-l-butanol, 1,1 -dimethyl- 1-butanol, pentanol, 1 -methyl- 1-butanol, 2-methyl-l-butanol, 3-methyl-l -butanol, 1 -ethyl- 1 -propanol, or 2-ethyl-l -propanol.
In a prefeπed embodiment, step (ii) is conducted initially at about -30 °C, then at about 25 °C for about one hour, then at about 90 °C for about eight hours in essentially z'sø-propanol.
In a preferred embodiment, step (jj) comprises isolating the compound having formula (28), or a therapeutically acceptable salt thereof, by crystallization.
In another part of the eighth embodiment of this invention, the compound having formula (28) is isopropyl (2R,5R)-5-((lR,25)-l-(acetylamino)-2-methoxy-2- methylpentyl)-4-((lZ)-l-propenyl-2 -pyπolidinecarboxylate and is isolated by crystallization of its αra-toluenesulfonate salt.
In still another part of the eighth embodiment of this invention, the isopropyl (2R,5R)-5-((lR,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-4-(( 1 Z)- 1 - propenyl)-2-pyπolidinecarboxylate, >αr -toluenesulfonate is crystallized from z'sø-propyl acetate. In still yet another part of the eighth embodiment of this invention, the crystallization comprises mixing a solution comprising essentially isopropyl (2R,5R)-5- (( 1 R,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-4-(( 1 Z)- 1 -propenyl)-2- pyπolidinecarboxylate in z'so-propyl acetate and a solution comprising essentially ra-toluenesulfonic acid monohydrate in wo-propyl acetate. In still yet another part of the eighth embodiment of this invention, the crystallization of isopropyl (2R,5R)-5-((lR,25)-l-(acetylamino)-2-methoxy-2- methylpentyl)-4-(( 1 Z)- 1 -propenyl)-2 -pyπolidinecarboxylate, /?αrα-toluenesulfonate is conducted at a solution temperature of between about 40 °C and about 70 °C, a prefeπed embodiment of which is between about 50 °C and about 60 °C, in which the temperature of the solution is lowered to about 25 °C at a rate of about 5 °C per hour to precipitate the isopropyl (2R,5R)-5-((lR,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-4-(( 1Z)- 1 - propenyl)-2-pyrrolidinecarboxylate,/?αra-toluenesulfonate salt before isolating the same.
In still yet even another embodiment of this invention are disclosed compounds which are useful as intermediates for the preparation of neuraminidase inhibitors, said compounds having structural formula (29)
Figure imgf000039_0001
structural formula (29-a)
Figure imgf000040_0001
(29-a),
structural formula (30)
Figure imgf000040_0002
(30), and structural formula (30-a)
Figure imgf000040_0003
(30-a), or salts thereof, in which the carbon-carbon double bond in the compounds having structural formulas (29), (29-a), (30), and (30-a) is substantially in the Z configuration, and in which
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
,2 .
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; 4 ■
R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl);
, 10
R is methyl, ethyl, iso-propyl, or vinyl;
, 13 •
R is alkoxy alkoxycarbonyl, and hydroxy;
R , 14 is hydrogen or tert-butoxycarbonyl; and
R , 15 is hydrogen or acetyl, with the proviso that R is alkoxycarbonyl only for the compound having structural formula (30-a), preferred embodiments of which include a compound having structural formula (29) or (29-a) in which R1 is alkyl; R2 is
4 14 15 alkyl; R is alkyl; R is hydrogen, and R is hydrogen; a compound having structural formula (29) or (29-a) in which R is alkyl; R is
4 14 15 alkyl; R is alkyl; R is hydrogen, and R is acetyl;
1 2 a compound having structural formula (29) or (29-a) in which R is alkyl; R is alkyl; R 4 is alkyl; R 14 is tert-butoxycarbonyl, and R 15 is acetyl;
1 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is tert-butoxycarbonyl, and R is hydrogen;
1 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is tert-butoxycarbonyl, and R is acetyl;
1 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is hydrogen, and R is hydrogen;
1 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is hydrogen, and R is acetyl;
1 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is tert-butoxycarbonyl, and R is hydrogen;
1 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is tert-butoxycarbonyl, and R is acetyl;
1 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is hydrogen, and R is hydrogen;
1 • 2 a compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is hydrogen, and R is acetyl; and a compound having structural formula (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxycarbonyl; R is hydrogen, and R is acetyl, of which the more prefeπed embodiments of the foregoing are the compound having structural formula (29) or (29-a) in which R 1 is alkyl; R 2 is alkyl; R is alkyl; R is hydrogen, and R is hydrogen;
1 2 the compound having structural formula (29) or (29-a) in which R is alkyl; R is alkyl; R is alkyl; R is hydrogen, and R is acetyl;
1 2 the compound having structural formula (29) or (29-a) in which R is alkyl; R is alkyl; R is alkyl; R is tert-butoxycarbonyl, and R is acetyl;
1 2 the compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is tert-butoxycarbonyl, and R is acetyl; the compound having structural formula (30) or (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is tert-butoxycarbonyl, and R is acetyl; and the compound having structural formula (30-a) in which R is alkyl; R2 is alkyl; R4 is alkyl; R is alkoxycarbonyl; R is hydrogen, and R is acetyl, and more prefeπed embodiments of which include a compound having structural formula (29) or (29-a) which is (45,5R)-5-((lR,25)-l-amino-2-methoxy-2-methylpentyl)-4-((lZ)-l-propenyl)-2- pyπolidinone; a compound having structural formula (29) or (29-a) which is N-((lR,25)-2-methoxy-2-methyl-l-((2R,35)-5-oxo-3-((lZ)-l-propenyl)pyπolidinyl)- pentyl)acetamide; a compound having structural formula (29) or (29-a) which is tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-oxo-3-((lZ)- 1 -propenyl)- 1 -pyrrolidinecarboxylate; a compound having structural formula (30) or (30-a) which is anomeric tert-butyl (2R,3S)-2-(( \R,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-5- hydroxy-3 -(( 1 Z)- 1 -propenyl)- 1 -pyrrolidinecarboxylate; a compound having structural formula (30) or (30-a) which is tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-methoxy-3- (( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate; and a compound having structural formula (30-a) which is isopropyl (2R,5R)-5-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-4-((lZ)-l- propenyl)-2 -pyπolidinecarboxylate, /jøra-toluenesulfonic acid salt.
It is meant to be understood that the term "substantially pure" means greater than 90% pure; preferably greater than 95% pure, and more preferably greater than 99% pure. It is also meant to be understood that the term "essentially," in reference to a solvent or solvents, means greater than 90% of that solvent or solvents; preferably greater than 95% of that solvent or solvents, and more preferably greater than 99% of that solvent or solvents. It is also meant to be understood that many of the compounds of this invention contain one chiral carbon atom and exist as enantiomers in the (R) or (S) configuration or as racemic mixtures comprising varying amounts of one enantiomer over the other. Mixtures comprising equimolar amounts of enantiomers are racemic mixtures and are designated (±). Mixtures comprising varying amounts of one enantiomer over the other are designated enantiomerically enriched with the enantiomer present in the higher amount. The enantiomeric enrichment of a mixture can be determined by gas or liquid chromatography in a chiral environment such as, for example, a column packed with a chiral auxiliary. Prefeπed enantiomeric enrichment for the purpose of this invention is about 86-89% enantiomeric excess of one enantiomer over the other. A more prefeπed enantiomeric enrichment for the purpose of this invention is about 94-97% enantiomeric excess of one enantiomer over the other. A still more prefeπed enantiomeric enrichment for the purpose of this invention is a substantially enantiomerically enriched mixture in which there is greater than a 99% enantiomeric excess of one enantiomer over the other.
It is also meant to be understood that many of the compounds of this invention which contain more than one chiral carbon atom exist as diastereomers. Diastereomeric enrichment or diastereomeric excess is determined by the enantiomeric excess of each chiral carbon atom in the diastereomer. Absolute stereochemistry is determined by the spatial orientation of each enantiomeric center relative to the other. The spatial orientation of each substituent relative to the other in a diastereomer can be predicted with a high degree of certainty by employing a substantially enantiomerically enriched starting materials such as, for example, the synthesis employing substantially enantiomerically enriched compound having formula (15-a) in step (x), also recited in the sixth embodiment of this invention. Prefeπed diastereomeric enrichment for the purpose of this mvention is an isolated yield of about 93:7 to about 95:5 mixture of diastereomers. A more preferred diastereomeric enrichment for the purpose of this invention is an isolated yield of about 99.1 :0.9 mixture of diastereomers. Because the diastereomers of this invention have different solubilities, they can be separated by column chromatography on silica gel as described in the 787 application or, more preferably, by crystallization.
It is also to be understood that the compound of this invention having structural formula (25) exists as anomers in which the chiral carbon atom of the pyπolidine ring bearing the hydroxy group exists as an equilibrium mixture of (R) and (S) isomers at that chiral carbon atom.
It is also meant to be understood that many of the compounds of this invention contain a carbon-carbon double bond and can therefore exist as geometric isomers. This invention contemplates the various geometric isomers and mixtures thereof resulting from the arrangement of substituents around a carbon-carbon double bond and designates such isomers as being in the Z or E configuration, in which the term "Z" represents the larger two of the four substituents disposed on same side of a carbon-carbon double bond and the term "E" represents the larger two of the four substituents on opposite sides of a carbon-carbon double bond. Prefeπed geometric isomeric enrichment for the purpose of this invention is a ratio greater than about 87: 13 Z/E. More preferred geometric isomeric enrichment for the purpose of this invention is a ratio of about 98.8: 1.2 Z/E. A still more prefeπed geometric isomeric enrichment for the purpose of this invention is a ratio of about 99.3:0.7 Z/E. Such preferred geometrically isomerically enriched compounds are defined as being substantially in the Z configuration.
It is also meant to be understood that the compounds of this invention can exist as therapeutically acceptable salts. The term "therapeutically acceptable salt" means salts or zwitterionic forms of the compounds which are water or oil-soluble or dispersible, which are suitable for inhibition of neuraminidases without undue toxicity, irritation, and allergic response, which are commensurate with a reasonable benefit risk ratio, and which are effective for their intended use. The salts can be prepared during the final isolation and purification of a compound having structural formula (28) by derivatization of the same as a salt such as citrate, aspartate, benzoate, benzenesulfonate, bisulfate, butyrate, camphorate, camphorsufonate, digluconate, formate, fumarate, glycerophosphate, hemisulfate, heptanoate, hexanoate, hydrochloride, hydrobromide, hydroiodide, lactate, maleate, mesitylenesulfonate, methanesulfonate, naphthylenesulfonate, nicotinate, oxalate, pamoate, pectinate, persulfate, 3-phenylpropionate, picrate, pivalate, propionate, succinate, tartrate, thiocyanate, trichloroacetic, trifluoroacetic, phosphate, glutamate, bicarbonate, />αra-toluenesulfonate, undecanoate, and the like.
In a prefeπed embodiment for the practice of this invention, the compound having structural formula (28) is prepared as the j?αrø-toluenesulfonate salt.
The invention will now be described in connection with certain specific embodiments which are not intended to limit its scope. On the contrary, the invention covers all alternatives, modifications, and equivalents which are included within the scope of the claims. Thus, the following examples will illustrate an especially preferred practice of the invention, it being understood that the examples are for the purposes of illustration of certain preferred embodiments and are presented to provide what is believed to be the most useful and readily understood description of its procedures and conceptual aspects.
Example 1 methyl (2E)-2-methyl-2-pentenoate A solution of (2E)-2-methyl-2-pentenoic acid (1027 g), triethylformate (1031 g), and concentrated H2SO4 (24 mL) in methanol (3.23L) was stiπed at reflux for 10 hours, cooled to ambient temperature, and treated with NaHCO3 (76 g). The methanol layer was isolated and distilled at 45 mm Hg to provide fractions which distilled at 38-42 °C and 68-72 °C, the latter of which provided 820 g of desired product. The 38-42 °C fraction was concentrated to one-quarter of its original volume and redistilled to provide an additional 200 g of the desired product (88.5% total) which azeotropes with methanol. Η NMR (CDC13) δ 6.8-6.72 (m, 1H), 3.73 (s, 3H), 2.5-2.2 (m, 2H), 1.83 (m, 3H), 1.04 (t, J=5.1 Hz, 3H). Example 2 (2E)-2-methyl-2-penten- 1 -ol A solution of IM diisobutylaluminum hydride in hexane (2.768Kg) at -60 °C was treated with Example 1 (230 g) over 45 minutes, stiπed for 1 hour, warmed to ambient temperature, added to a slurry of ice (1.3Kg) and 50% (w/w) aqueous NaOH (1.3Kg) over 1 hour, stiπed for 2 hours at 0 °C, and warmed to ambient temperature over 18 hours. The hexane layer was isolated and concentrated, and the concentrate was fractionally distilled at 50 mm Hg to provide 160 g (89%) of the desired product as a fraction which distilled at 82-84 °C. Η NMR (CDC13) δ 5.44-5.38 (m, IH), 3.96 (d, J=5.42 Hz, 2H), 2.1-2.0 (m, 2H), 1.65 (s, 3H), 0.96 (t, J=5.09 Hz, 3H).
Example 3 3 ,4-anhvdro- 1 ,2-dideoxy-4-methyl-D-threo-pentitol A slurry of powdered 4A sieves (81 g) in dichloromethane (2.7L) at -20 °C was treated sequentially with dimethyl D-tartrate (102.4 g), titanium z'so-propoxide (159 g), and Example 2 (180 g) in dichloromethane (315 mL), stiπed for 20 minutes, cooled to -40 °C, treated with pre-dried (4 A sieves) 5-6M tert-butyl hydroperoxide in decane (719 mL), stiπed for 2 hours, treated with dimethyl sulfide (90 mL) and 30% (w/w) aqueous NaOH (750 mL), stiπed for 2 hours, warmed to 15 °C, and treated with water (IL). The aqueous layer was isolated and extracted with dichloromethane (IL). The organics were combined and concentrated to provide 104 g (50%) of the desired product (and some decane), which was used directly in the next step. *H NMR (CDC13) δ 3.8-3.6 (m, IH), 3.0 (t, J=6.3 Hz, 2H), 1.7 (m, IH), 1.7-1.53 (m, 2H), 1.29 (s, 3H), 1.04 (t, J=7.8 Hz, 3H).
Example 4 (25)-2-methyl- 1 ,2-pentanediol A solution of IM lithium aluminum hydride in THF (3.59L) at -40 °C was treated with a solution of Example 3 (104 g) in THF (300 mL) over 2 hours, warmed to ambient temperature over 18 hours, cooled to -20 °C, treated sequentially with water (100 mL), 15% (w/w) aqueous NaOH (100 mL), and water (150 mL), each over 1 hour, stiπed for 2 hours while warming to 10 °C, filtered through diatomaceous earth (Celite ), and concentrated. The concentrate was fractionally distilled at 45 mm Hg to provide 105.1 g (50%, two steps) of the desired product (85-93% ee) as a fraction which distilled at 128-130 °C. 'H NMR (CDCI3) δ 3.5-3.38 (m, 2H), 1.5-1.31 (m, 4H), 1.17 (s, 3H), 0.94 (t, J=7.1 Hz, 3H). Example 5 ((((25)-2-methoxy-2-methylpentyl)oxy)methyl)benzene A suspension of dry sodium hydride (prepared by washing 6.18 g of 60% oily sodium hydride with heptane (2x 200 mL)) in THF at 0 °C was treated sequentially with a solution of Example 4 (82.4 g) in THF (50 mL) over 30 minutes and benzyl bromide (90.6 mL) over 30 minutes, stirred for 12 hours at ambient temperature, cooled to 0 °C, treated with methyl iodide (272 mL), stirred for 18 hours at ambient temperature, and treated with water (500 mL) and methyl tert-butyl ether (500 mL). The organic layer was isolated and concentrated. The concentrate was treated sequentially with with ΛyV-dimethyl ethylenediamine (18.5 g), water (IL) and methyl tert-butyl ether (IL). The organic layer was isolated, washed with IM HC1 (100 mL) and 3% (w/w) aqueous sodium chloride (200 mL) and concentrated to provide 145 g (93.5%) of the desired product, which was used directly in the next step. Η NMR (CDC13) δ 7.35-7.26 (m, 5H), 4.55 (s, 2H), 3.32 (dd, J=9.8 and 12.5 Hz, 2H), 3.22 (s, 3H), 1.58-1.42 (m, 2H), 1.34-1.22 (m, 2H), 1.14 (s, 3H), 0.9 (t, J=7.1 Hz, 3H).
Example 6 (25)-2-methoxy-2-methyl- 1 -pentanol A solution of Example 5 (99.5 g) in THF (650 mL) at ambient temperature was treated with 5% palladium hydroxide on carbon (13 g), stiπed under hydrogen at 40 pounds per square inch for 18 hours, and filtered through diatomaceous earth (Celite ). The filtrate was treated with 5% palladium hydroxide on carbon (13 g), stiπed under hydrogen at 40 pounds per square inch for 1 hour, filtered through diatomaceous earth (Celite ), and concentrated. The concentrate was fractionally distilled at 50 mm Hg, and fractions which distilled at 80-90 °C and 120-140 °C were collected and combined to provide 48.9 g (82.7%) of the desired product and some toluene. !H NMR (CDCI3) δ 3.55 (q, J=l l . l Hz, 2H), 3.3 (s, 3H), 1.6-1.44 (m, 4H), 1.2 (s, 3H), 1.03 (t, J=7.4 Hz, 3H).
Examples 7-10 describe an alternate synthesis of Example 6.
Example 7 2-methoxy-2-methylpentanoic acid A solution of 2-pentanone (2Kg) and bromoform (61Kg) in methanol (6.3Kg) at 0 °C with overhead stirring was treated with a solution of potassium hydroxide (10.6Kg) in methanol (19Kg) over 5 hours, filtered, and concentrated. The concentrate was treated with 20%) (w/w) aqueous sodium hydroxide to pH 9. The aqueous layer was isolated, stiπed at 50 °C for 2 hours, cooled to ambient temperature, washed with methyl tert-butyl ether (3L), cooled to 5 °C, acidified with concentrated HCl to pH 2-3, and extracted with methyl tert-butyl ether (18L). The extract was washed with 10% (w/w) aqueous sodium chloride (3L) and concentrated to provide 2.6Kg (77%) of the desired product which was used directly in the next step. H NMR (CDC13) δ 11.6 (s, IH), 3.26 (s, 3H), 1.39 (s, 3H), 1.8-1.23 (m, 4H), 0.89 (t, 3H, J=7.0 Hz).
Example 8 methyl 2-methoxy-2-methylpentanoate A solution of Example 7 (2.5Kg) in methanol (12L) at ambient temperature was treated with concentrated sulfuric acid (200 mL), heated to reflux for 16 hours, cooled to ambient temperature, treated with sodium bicarbonate (1.5Kg), and concentrated. The concentrate was dissolved in methyl tert-butyl ether (8L), extracted with water (4L) and saturated aqueous Na2CO3 (100 mL), and concentrated. The concentrate was distilled at 50 mm Hg, and a fraction boiling at 90-95 °C was collected to provide 2.1 Kg (77%) of the ddeessiirreedd pprroodduucctt.. !!HH NNMMRR ((CCDDCCII33)) δδ 33..77 ((ss,, 33H), 3.25 (s, 3H), 1.7-1.6 (m, 2H), 1.35 (s, 3H), 1.3-1.15 (m, 2H), 0.89 (t, 3H, J=7.0 Hz).
Example 9 (25)-2-methoxy-2-methylpentanoic acid Candida Ruglosa (20 g, 875 units/mg) was treated sequentially with 0.05M phosphate buffer (pH 8) and a solution of Example 8 (20 g) in acetone (50 mL), heated at 37 °C for 116 hours with a pH adjustment to 4.5-6 with 2M NaOH after 74 hours, acidified to pH 2 with 2M HCl, and extracted with ethyl acetate (500 mL). This extract was extracted with 10% (w/w) aqueous Na2CO3 (200 mL and 100 mL), and the combined aqueous extracts were acidified to pH 3 with concentrated HCl and extracted with methyl tert-butyl ether (300 mL). This extract was dried (Na2SO ), filtered, and concentrated to provide 8.5 g (93% recovery, >99% ee) of the desired product, which was used directly in t thhee nneexxtt sstteepp.. ΗΗ NNMMRR ((CCDDCCII33)) δδ 33..4433 ((qq,, j J=12 Hz, 2H), 3.2 (s, 3H), 1.52-1.4 (m, 2H), 1.22-1.1 (m, 2H), 1.18 (s, 3H), 0.94 (s, 3H).
Example 10 (25)-2-methoxy-2-methyl- 1 -pentanol A solution of Example 9 (507 g) in dichloromethane (3L) at 0 °C was treated with 10M borane-dimethyl sulfide (624 mL), stiπed for 5 hours at ambient temperature, cooled to 0 °C to 5 °C, treated with 2M NaOH (3.3L), warmed to ambient temperature and stirred for several hours. The layers were separated, and the water layer was extracted with dichloromethane (2x 1.6L). The combined extracts were washed with 2M NaOH (1.65L) and 10%) (w/w) aqueous NaCl (1.65L), dried (MgSO ), filtered, and concentrated to provide 460 g (100%) of the desired product, which was used directly in the next step. 'H NMR (CDC13) δ 3.55 (q, J=l l.l Hz, 2H), 3.3 (s, 3H), 1.6-1.44 (m, 4H), 1.2 (s, 3H), 1.03 (t, J=7.4 Hz, 3H).
Example 11 (25)-2-methoxy-2-methylpentanal A solution of Example 8 (19.21 g) and triethylamine (60 mL) in dichloromethane (40 mL) at 0 °C was treated with sulfur trioxide-pyridine (35 g) in DMSO (160 mL) over 2.5 hours, stiπed for 30 minutes, and treated with 2M H3PO4 (325 mL) over 30 minutes. The aqueous layer was isolated and extracted with dichloromethane (160 mL), and the combined organics were washed with 2M H3PO4 (325 mL), dried (flash silica), filtered, and concentrated with intermittent dichloromethane treatment to provide 69.43 g of a 29.7%) (w/w) solution of the desired product (97.8%>), which was used directly in the next step. H NMR (CDC13) δ 9.58 (s, IH), 3.28 (s, 3H), 1.58 (m, 2H), 1.29 (m, 2H), 1.22 (s, 3H), 0.92 (t, J=7.4 Hz, 3H).
Example 12 ( 1 E,25)-2-methoxy-2-methylpentanal 5-tritylthioxime The solution of the 29.7% (w/w) solution of Example 11 in dichloromethane
(60.24 g) at ambient temperature was treated sequentially with triphenylmethanesulfenamide (39.03 g), pyridiniumpαrα-toluenesulfonate (688 mg), and sodium sulfate (9.81 g), stiπed for 18 hours, treated with heptane (32 mL), stiπed for 5 minutes, and filtered. The filtrate was concentrated with intermittent heptane treatment to provide 80 g of a 64% (w/w) solution of the desired product in heptane. This solution was filtered through a silica gel plug (prepared from flash silica gel (64 g) and heptane in a 150 mL filter funnel with a 9 cm diameter and 3 cm height) with 5% methyl tert-butyl ether/heptane (512 mL). The filtrate was concentrated to provide 101.9 g of a solution of 50% (w/w) of the substantially enantiomerically enriched desired product (93%), which wwaass uusseedd ddiirreeccttllyy iinn tthhee nneexxtt sstteepp.. ! HH NNMMRR ((CCDDCCI133)) δδ 7.56 (s, IH), 7.28 (m, 15H), 2.96 (s, 3H), 1.35 (m, 2H), 1.16 (m, 2H), 0.80 (t, J=7.4 Hz).
Example 13 tert-butyl-4-hvdroxy-2-oxo-pyπolidinecarboxylate A solution of 4-amino-3-hydroxy-«-butyric acid (25 g) in pyridine (125 mL) was treated with hexamethyldisilazane (71.5 mL) and xylenes (250 mL), stiπed at reflux for 16 hours, concentrated to 50 mL, cooled to 3 °C, treated sequentially with 4-dimethylaminopyridine (1.22 g) in THF (40 mL) and di-tert-butyldicarbonate (54.96 g) in THF (80 mL), stirred for 14 hours at ambient temperature, treated with triethylamine trihydrofluoride (15 mL), stiπed for 2 hours, treated with heptane, cooled to 3 °C, and filtered. The filtrant was washed with heptane (150 mL) and dried under vacuum at 50 °C to provide 41 g (97%) of the desired product. !H NMR (CDC13) δ 4.37 (m, IH), 3.65 (dd, J=5.5, 11.4 Hz, IH), 3.63 (ddd, J=l .l, 3.3, 11.8 Hz, IH), 2.71 (dd, J=6.2, 17.3 Hz, IH), 2.47 (ddd, J=l . l, 3.6, 17.2 Hz), 1.53 (s, 9H).
Example 14 tert-butyl 2-oxo-3-pyπoline carboxylate A solution of Example 13 (3.2Kg) in THF (31.26Kg) was treated with triethylamine (4.425Kg), cooled to 0.8 °C, treated with methanesulfonyl chloride (2.32Kg) over 2 hours, stirred for an additional 2 hours, treated with ethyl acetate (40L), and filtered. The filtrate was washed with 15%> (w/w) aqueous NaCl (2x 13L), and the combined washings were extracted with isopropyl acetate (13.3L). The filtrant was rinsed with isopropyl acetate (13.3L), and the organics were combined and concentrated to 20L with intermittent heptane treatment (4x 20L) to keep its volume at 30L during distillation. The concentrate was treated with dichloromethane (12L) to provide a solution of 2.5369Kg of the desired product (88.6%), which was used directly in the next step. H NMR (CDCI3) δ 7.18 (dt, J=6.2, 1.9 Hz, IH), 6.16 (dt, J=6.2, 1.9 Hz, IH), 4.35 (t, J=1.9, 2H), 1.56 (s, 9H).
Example 15 tert-butyl 2-((tert-butyl(dimethyl')silyl oxy - 1 H-pyπole- 1 -carboxylate
® Diatomaceous earth (Celite , 3.3Kg) was treated sequentially with the solution of
Example 14 (2.506Kg), dichloromethane (25L), and heptane (25.8L). The resulting solution slurry was treated with triethylamine (4.5Kg), cooled to 0 °C, and treated with tert-butyldimethylsilyl trifluoromethanesulfonate (4.71 Kg) over 2 hours, stiπed for 1 hour, treated with methanol (IL) over 10 minutes, stiπed for an additional 20 minutes, concentrated to 20L with intermittent heptane treatment (3x 20L), filtered, concentrated to 7.913Kg, and treated with heptane (3.5Kg) to provide 11.41Kg of a 39.3% (w/w) solution of the desired product (96.5%), which was used directly in the next step. H NMR (CDCI3) δ 6.69 (dd, J=2.2, 4.0 Hz, IH), 5.90 (dd, J=3.7, 4.0, IH), 5.23 (dd, J=2.2, 3.7 Hz, IH), 1.57 (s, 9H), 0.99 (s, 9H), 0.22 (s, 6H).
Example 16 tert-butyl (2R)-2-(dR.25)-2-methoxy-2-methyl-l-(ftritylsulfanvnamino pentyl)-5-oxo- 2.5 -dihydro- 1-1 H-pyπole- 1 -carboxylate A solution of 44.8% (w/w) of Example 12 iri heptane (2.534Kg) was treated with the solution of 39.9% (w/w) of Example 15 in heptane (3.068Kg) and THF (14.54Kg), cooled to -40 °C, and treated with trifluoromethanesulfonic acid (320 g) over 40 minutes with additional trifluoromethanesulfonic acid (11 mL, 5.5 mL, and 22 mL) added at 1, 2, and 4.5 hour intervals, respectively. After the last addition, the solution was stiπed for 1 hour at -40 °C, washed with 0.5M NaHCO3 (16.3Kg) and brine (3.8Kg), treated with heptane (3.15Kg), and concentrated with intermittent heptane treatment (3.2Kg, 4.3Kg, 1.6Kg, and 5.6Kg) to keep its volume at 8L during the distillation. A solid that precipitated from the mother liquor during the distillation was filtered and dried under vacuum at 50 °C to provide 1.353Kg (82%) of the diastereomerically enriched desired product. !H NMR (CDC13) δ 7.22 (dd, J=2.2, 6.2 Hz, IH), 7.14 (m, 15H), 5.92 (dd, J=1.5, 6.3 Hz, IH), 4.73 (m, IH), 3.76 (dd, J=2.9, 11.4 Hz, IH), 2.95 (s, 3H), 2.52 (d, J=11.4 Hz, IH), 1.47 (m, 3H), 1.26 (s, 9H), 1.20 (m, 3H), 0.98 (m, IH), 0.82 (t, J=6.6 Hz, 3H).
Example 17 tert-butvU2R.35)-2-fπR.25)-2-methoxy-2-methyl-l-(ftritylsulfanyl)amino)pentyl)-5-oxo-
3 -(( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate A suspension of copper(I) bromide dimethylsulfide complex (8.74 g) in THF
(750 mL) at -30 °C was treated with 0.485M 1 -propenyl magnesium bromide in THF (526 mL) over 15 minutes and trimethylsilyl chloride (11.09 g) over 5 minutes, stirred for another 15 minutes, warmed to -25 °C, treated with Example 16 (50 g) in toluene (750 mL) over 20 minutes, stiπed for another 5 minutes, treated with a solution comprising water (75 mL), concentrated NH4OH (75 mL), and 25%> (w/w) aqueous NH4C1 (600 mL), warmed to ambient temperature, and stiπed for 1 hour. The organic layer was isolated and washed with a solution comprising water (75 mL), concentrated NH4OH (75 mL), 25% (w/w) and aqueous NH4C1 (600 mL), and then with brine (600 mL) to provide a solution of the desired product, in substantially in the Z configuration, which was used directly in the next step. !H NMR (CDCI3) δ 7.33-7.15 (m, 15H), 5.38 (m, 2H), 3.99 (d, J=1.4 Hz, IH), 3.71 (t, J=9.2 Hz, IH), 3.59 (dd, J=2.2, 10.3 Hz, IH), 3.06 (d, J=10.6 Hz, IH), 3.03 (s, 3H), 2.81 (dd, J=9.6, 17.6 Hz, IH), 1.95 (dd, J=1.5, 17.6, IH), 1.57 (d, J=5.1 Hz, 3H), 1.52 (m, IH), 1.47 (m, IH), 1.43 (s, 9H), 1.09 (m, 2H), 0.86 (t, J=6.7 Hz, 3H), 0.50 (s, 3H).
Example 18 (45.5R -5-(("lR.25)-l-ammo-2-methoxy-2-methylpentvn-4-("αZ)-l-propenyl)-2- pyπolidinone
The solution of Example 17 was cooled to -20 °C, treated sequentially with HCl gas (100 g) over 1 hour, stiπed for an additional 10 minutes, treated with diatomaceous
® earth (Celite , 50 g), stiπed for 5 minutes, concentrated to 500 mL, treated with water (200 mL) and toluene (200 mL), and filtered. The organic layer was isolated and extracted with water (100 mL). The extracts were combined and washed with toluene (200 mL) to provide a solution of the desired product, which was used directly in the next step.
Example 19 N-((lR.25)-2-methoxy-2-methyl-l-('(2R.35)-5-oxo-3-f(lZ)-l- propenyl)ρyπolidinyl)pentyl)acetamide The combined aqueous extracts from Example 18 were treated with 50%> (w/w) aqueous NaOH (17 mL) to pH 14 and acetic anhydride (16.62 g and 1.48 g), with additional 50%> NaOH added to maintain the pH of the solution at 12, stirred for 5 minutes, and treated with sodium chloride (7 g). The organic layer was isolated, and the water layer was extracted with isopropyl acetate (2x 200 mL). The organics were combined and concentrated with sequential, intermittent isopropyl acetate (3x 200 mL) and THF (250 mL) treatment to provide the desired product, which was used directly in the next step. lH NMR (CDC13) δ 6.44 (br s, IH), 5.50 (m, IH), 5.39 (ddq, J=9.2, 10.7, 1.5 Hz, IH), 4.26 (dd, J=8.1, 10.3 Hz, IH), 3.51 (dd, J=6.6, 8.1 Hz, IH), 3.30 (ddd, J=6.9, 9.1 , 16.1 Hz, IH), 3.18 (s, 3H), 2.45 (dd, J=10.2, 16.9 Hz, IH), 1.99 (dd, J=8.9, 16.9 Hz, IH), 1.95 (s, 3H), 1.62 (dd, J=1.5, 6.7 Hz, 3H), 1.44 (m, 2H), 1.43 (br s, IH), 1.25 (m, 2H), 1.11 (s, 3H), 0.89 (t, J=7.0 Hz, 3H).
Example 20 tert-butyl (2R,35)-2-((lR.25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-oxo-3-((lZ)-
1 -propenyl)- 1 -pyrrolidinecarboxylate A solution of the concentrate from Example 19 in THF (250 mL) was treated sequentially with triethylamine (23.5 mL), TvJV-dimethylaminopyridine (0.51 g), and di- tert-butyldicarbonate (27.43 g) in THF (20 mL), stirred for 3.5 hours, cooled to -10 °C, and treated with 0.5M HCl (310 mL) over 25 minutes. The water layer (pH 6.44) was isolated and extracted with isopropyl acetate (2x 200 mL). The organics were combined, washed with 23%> (w/w) aqueous NaCl, concentrated to 100 mL, treated with isopropyl acetate (300 mL), concentrated to 200 mL, treated with heptane (200 mL), and concentrated to 50-60 mL to provide a slurry. The slurry was stirred for 20 minutes at ambient temperature and filtered with cold (0 °C) 1 : 1 heptane/isopropyl acetate (2x 100 mL) rinsing. The filtrant was dried under vacuum at 50 °C to provide 26.80 g (82%, 4 steps) of the desired product. *H NMR (CDC13) δ 5.94 (br d, J=9.2 Hz, IH), 5.45 (m, 2H), 4.55 (dd, J=2.5, 9.5 Hz, IH), 4.03 (dd, J=0.7, 2.6 Hz, IH), 3.81 (dt, J=0.7, 9.2 Hz,
IH), 3.24 (s, 3H), 2.78 (dd, J=9.5, 18.0 Hz, IH), 2.06 (dd, J=1.5, 18 Hz, IH), 2.00 (s, 3H), 1.79 (dd, J=8.8, 12.8 Hz, IH), 1.71 (m, 2H), 1.67 (d, J=5.1 Hz, IH), 1.60 (m, 2H), 1.58 (s, 9H), 1.27 (dd, J=7.0, 8.8 Hz, IH), 1.16 (s, 3H), 0.95 (t, J=6.9 Hz, 3H).
Example 21 2: 1 anomeric tert-butyl (2R.35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5- hydroxy-3 -(( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate
A solution of Example 20 (50.0 g) in THF (500 mL) at -13.5 °C with overhead
® stirring was treated with IM lithium triethylborohydride (Superhydride , 157 mL) over
30 minutes, stiπed for an additional 15 minutes, treated with methanol (75 mL) over 5 minutes, stiπed for an additional 5 minutes at -5 °C, warmed to 17 °C, stiπed for 30 minutes, concentrated to 200 mL, treated with THF (500 mL), concentrated to 100 mL, and added to 5% (w/w) aqueous KH2PO . The organic layer was isolated and washed with 12%) (w/w) aqueous NaCl (750 mL) to provide a solution of 48.77 g (97%>) of desired product, which was used directly in the next step.
Example 22 tert-butyU2R.35)-2-((lR.25)-l-(acetylamino)-2-methoxy-2-methylpentyl -5-methoxy-3- (( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate The solution of Example 21 was concentrated twice to 100 mL with a methanol treatment (500 mL) between the concentrations then concentrated to 176.1 g after a final methanol (500 mL) treatment. The concentrate was treated with methanol (90 mL), trimethylorthoformate (50 mL), and camphor sulfonic acid (1.41 g), stirred for 1 hour, treated with 5% (w/w) aqueous KHCO3, and extracted with isopropyl acetate (IL). The extract was washed with 23% (w/w) aqueous NaCl, concentrated twice to 150 mL with an intermittent acetonitrile treatment (500 mL), concentrated to 150.57 g after a acetonitrile (500 mL) treatment, and treated with acetonitrile (370 mL) to provide 435.5 g of a 11.2% (w/w) solution of the desired product (97.5%), which was used directly in the next step. !H NMR (CDCI3) δ 5.98 (br d, J=9.9 Hz, IH), 5.43 (m, IH), 5.31 (m, IH), 5.17 (d, J=5.5 Hz, 0.5H), 5.01 (d, J=5.1 Hz, 0.5H), 4.72 (dd, J=2.2, 9.9 Hz, IH), 3.93 (dd, J=3.0, 8.1 Hz, 0.5H), 3.82 (dd, J=2.9, 7.7 Hz, 0.5H), 3.33 (s, 1.5H), 3.30 (s, 1.5H), 3.06 (s, 3H), 2.05 (s, 1.5H), 2.03 (s, 1.5H), 1.97 (m, 2H), 1.88 (m, 1H),1.79 (m, 2H), 1.63 (dd,
J=1.5, 6.6 Hz, 3H), 1.56 (s, 4.5H), 1.52 (m, IH), 1.49 (s, 4.5H), 1.23 (m, IH), 1.12 (s, 3H), 0.95 (t, J=6.9 Hz, 3H).
Example 23 tert-butyl (2R.3S.5R)-2-(( 1R.25)- 1 -(acetylamino -2-methoxy-2-methylpentyl)-5-cvano-3- (( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate
A solution 13% (w/w) of Example 22 in acetonitrile (153.66 g) was treated with acetonitrile (23.83 g), cooled to -20 °C, treated with trimethylsilylcyanide (15.19 g), cooled to -40 °C, treated with trifluoromethanesulfonic acid (10.95 g) over 30 minutes, stirred an additional 3 hours, and added to a mixture of 10%> (w/w) aqueous K2CO3 (400 mL) containing 7.76 g NaOH and isopropyl acetate (400 mL). The extract was separated, washed sequentially with 23% (w/w) aqueous NaCl and 23% (w/w) aqueous NaCl containing KH2PO4 (2.82 g) and Na2HPO4-7H2O (7.12 g), concentrated to 50 mL with intermittent isopropyl alcohol treatment (3x 400 mL), and treated with isopropyl alcohol to provide 95.74 g of a 17.2% (w/w) solution of the desired product (86.9%), which was used directly in the next step. Η NMR (CDCI3) δ 5.93 (br d, J=9.2 Hz, IH), 5.72 (m, IH), 5.50 (m, IH), 4.55 (dd, J=1.5, 9.2 Hz, IH), 4.42 (ddd, J=l.l, 9.5, 27.2 Hz, IH), 3.89 (d, J=1.4 Hz, IH), 3.75 (m, IH), 3.20 (s, 3H), 2.50 (ddd, J=7.7, 9.1, 17.2 Hz, IH), 2.00 (s, 3H), 1.95 (d, J=13.2 Hz, IH), 1.72 (m, IH), 1.69 (m, IH), 1.66 (dd, J=1.8, 7.0 Hz, 3H), 1.55 (s, 9H), 1.30 (m, IH), 1.21 (m, IH), 1.13 (s, 3H), 0.95 (t, J=6.6 Hz, 3H).
Example 24 isopropyl (2R.5R)-5-(dR.25)-l-(acetylamino)-2-methoxy-2-methylpentvn-4-((lZ)-l- propenyl)-2-pyHolidinecarboxylate, para-toluenesulfonic acid salt
A solution of 20% (w/w) of Example 23 in isopropyl alcohol (231.43 g) was treated with isopropyl alcohol (44.43 g), cooled to -30 °C, treated with HCl gas
(100-200 g) over 23 minutes, warmed to ambient temperature over 1 hour, treated with isopropyl alcohol (235 g), refluxed for 8 hours, cooled to ambient temperature, and concentrated twice to one-half of its original volume with one intermittent isopropyl alcohol treatment (245 mL). The concentrate was added to 15% (w/w) aqueous KHCO3 (689 g) with isopropyl acetate (248 g) and water (50 g) rinsing and stirred for 15 minutes. The organic layer was isolated and washed with 15% (w/w) aqueous KHCO3 (376 g). The aqueous washings were combined and extracted with isopropyl acetate (160.9 g), and the combined organic extracts were washed with 20% (w/w) aqueous NaCl (300 g) and concentrated twice to one-quarter of their original volume with an intermittent isopropyl acetate treatment (374 g). This concentrate was filtered with isopropyl acetate (427 g) rinsing. The filtrate was treated with isopropyl acetate (843.56 g), warmed to 50-60 °C, and treated with a solution ofpαra-toluenesulfonic acid monohydrate (24.07 g) in isopropyl acetate (256.7 g) at 50-60 °C, stiπed for 50 minutes, cooled to ambient tremperature at 5 °C/hour, and filtered with isopropyl acetate (2x 200 g) rinsing. The filtrant was dried under vacuum at 40 °C to provide 53.78 g (94.7%) of the desired product. Η NMR (D2O) δ 7.73 (d, J=8.5 Hz, 2H), 7.41 (d, J=8.5 Hz, 2H), 5.69 (ddq, J=7.0, 11.0, 1.1 Hz, IH), 5.33 (ddq, J=9.2, 11.0, 1.9 Hz, IH), 5.16 (septet, J=6.2 Hz, IH), 4.49 (dd, J=7.7, 9.5 Hz, IH), 4.43 (d, J=10.3 Hz, IH), 3.75 (t, J=10.0 Hz, IH), 3.28 (s, 3H), 3.25 (m, IH), 2.66 (dt, J=13.6, 7.7 Hz, IH), 2.44 (s, 3H), 2.00 (s, 3H), 1.82 (dt, J=13.6, 10.3 Hz, IH), 1.68 (m, IH), 1.61 (dd, J=1.9, 7.0 Hz, 3H), 1.41 (m, IH), 1.34 (d, J=6.3 Hz, 3H), 1.33 (d, J=6.3 Hz, 3H), 1.30 (m, 2H), 1.27 (s, 3H), 0.88 (t, J=7.0 Hz, 3H). It will be evident to one skilled in the art that the processes and compounds of this invention are not limited to the forgoing examples, and that these processes and compounds can generally be embodied in other specific forms without departing from the essential attributes thereof, namely by substitution of the appropriate reactants and agents. Thus, it is desired that the examples be considered as illustrative and not restrictive, reference being made to the claims and not the foregoing examples, and that all changes which come within the meaning and range of equivalency of the claims be embraced therein.

Claims

WHAT IS CLAIMED IS:
A process for making a compound having structural formula (5) R1^ ^OH
R2 OH
(5), in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; and
2 R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl, comprising, in toto, the steps of:
(c) reacting a compound having structural formula (3)
Figure imgf000055_0001
(3), and a titanium z'sø-propoxide- dialkyl tartrate complex;
(d) reacting the product of step (c) and tert-butyl hydroperoxide to provide a compound having structural formula (4),
Figure imgf000055_0002
(4),
(e) reacting the product of step (d) and a second reducing agent to provide the compound having structural formula (5);
and (f) optionally isolating the compound having structural formula (5).
2. The process of claim 1 in which steps (c) and (d) are conducted sequentially.
3. The process of claim 1 in which steps (d) and (e) are conducted continuously.
4. The process of claim 1 in which the compound having the structural formula (4) has the stereochemistry illustrated by a compound having structural formula (4-a)
Figure imgf000056_0001
(4-a), and the compound having the structural formula (5) has the stereochemistry illustrated by a compound having structural formula (5-a)
Figure imgf000056_0002
(5-a).
5. The process of claim 1 in which the compound having the structural formula (3) is substantially pure
(2E)-2-methyl-2-penten- 1 -ol; the compound having the structural formula (4) is substantially pure, enantiomerically enriched
3 ,4-anhydro- 1 ,2-dideoxy-4-methyl-D-threo-pentitol; and the compound having the structural formula (5) is substantially pure, enantiomerically enriched
(25)-2-methyl- 1 ,2-pentanediol.
6. The process of claim 1 further comprising making the compound having formula (3) comprising, in toto, the steps of:
(a) reacting a compound having structural formula (1)
Figure imgf000056_0003
(1), a first acid, a first esterifying agent, and, optionally, a trialkylorthoformate to provide a compound having structural formula (2)
Figure imgf000056_0004
(2), in which R is C1-C4 alkyl; and
(b) reacting the product of step (a) and a first reducing agent to provide the compound having structural formula (3).
7. A process for making a compound having structural formula (12)
R 1 AT "OH
R'
(12), in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; and R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl), comprising, in toto, the steps of:
(g) reacting a compound having structural formula (5)
R1^^^^OH
R2 OH (5), a first base, and a selectively removable hydroxy protecting group precursor to provide a compound having structural formula (6)
Figure imgf000057_0001
(6), in which P is a selectively removable hydroxy protecting group;
(h) reacting the product of step (g), an alkylating agent, and the first base to provide a compound having structural formula (7)
Figure imgf000057_0002
(7);
(i) reacting the product of step (h) and a hydroxy protecting group removal agent to provide the compound having structural formula (12); and
(j) optionally isolating the compound having structural formula (12).
8. The process of claim 7 in which steps (g) and (h) are conducted sequentially.
9. The process of claim 7 in which steps (h) and (i) are conducted continuously.
10. The process of claim 7 in which the compound having the structural formula (5) has the stereochemistry illustrated by a compound having structural formula (5-a)
Figure imgf000058_0001
(5-a), the compound having the structural formula (6) has the stereochemistry illustrated by a compound having structural formula (6-a)
Figure imgf000058_0002
(6-a), the compound having the structural formula (7) has the stereochemistry illustrated by a compound having structural formula (7-a)
Figure imgf000058_0003
(7-a), and the compound having the structural formula (12) has the stereochemistry illustrated by a compound having structural formula (12-a)
Figure imgf000058_0004
11. The process of claim 7 in which the compound having the structural formula (5) is substantially pure, enantiomerically enriched
(25)-2-methyl- 1 ,2-pentanediol; the compound having the structural formula (6) is substantially pure, enantiomerically enriched
(25)- 1 -(benzyloxy)-2-methyl-2-pentanol; the compound having the structural formula (7) is substantially pure, enantiomerically enriched
((((25)-2-methoxy-2-methylpentyl)oxy)methyl)benzene; and the compound having the structural formula (12) is substantially pure, enantiomerically enriched
(25)-2-methoxy-2-methyl- 1 -pentanol.
12. A process for making an enantiomerically enriched compound having structural formula (12-b)
Figure imgf000059_0001
having the stereochemistry illustrated therein, in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; and
2
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl, comprising, in toto, the steps of:
(m) reacting a compound
Figure imgf000059_0002
(10), in which R is alkyl, C2-C4-haloalkyl, cycloalkylalkyl, or arylalkyl, and an esterase to provide either an enantiomerically enriched compound having structural formula (11-a)
Figure imgf000059_0003
(11-a) or an enantiomerically enriched compound having structural formula (11 -b)
Figure imgf000060_0001
(11-b);
(n) reacting the compound having structural formula (11-a) or the compound of (11-b) and a third reducing agent to provide the compound having structural formula (12-b);
and (o) optionally isolating the compound having structural formula (12-b).
13. The process of claim 12 in which steps (m) and (n) are conducted continuously.
14. The process of claim 12 in which the compound having the structural formula (10) is substantially pure methyl 2-methoxy-2-methylpentanoate; the compound having the structural formula (11) is substantially pure, enantiomerically enriched
(25)-2-methoxy-2-methylpentanoic acid; and the compound having the structural formula (12-b) is substantially pure, enantiomerically enriched
(25)-2-methoxy-2-methyl- 1 -pentanol.
15. The process of claim 12 further comprising making the compound having formula structural (10) comprising, in toto, the steps of: (k) reacting a compound having structural formula (8)
R1
>=0 R2
(8), bromoform, potassium hydroxide, and methanol to provide a compound having structural formula (9)
Figure imgf000061_0001
(9);
and
(1) reacting the product of step (k), a second esterifying agent and, optionally, an esterification promotion agent to provide the compound having structural formula (10).
16. A process for making a compound having structural formula (15)
Figure imgf000061_0002
(15), in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2 . R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
4 R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl);
L1 is N(R7), O, S, S(O), or S02;
R is aryl, furanyl, or, thienyl in which the aryl, the furanyl, and the thienyl are unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and η
R is hydrogen, alkyl, aryl, or />αra-toluenesulfonyl. comprising, in toto, the steps of: (p) reacting a compound having structural formula (12)
Figure imgf000061_0003
(12), an oxidant, a second base, and, optionally, a first additive, in which the oxidant, the second base, and the first additive are substantially soluble in the solvent or solvents in which this step is conducted, to provide a compound having structural formula (13)
Figure imgf000061_0004
(13);
and
(q) reacting the product of step (p), a compound having structural formula (14) H2N^ "C(R6)3
(14), a drying agent, and, optionally, a first acid catalyst to provide the compound having structural formula (15).
17. The process of claim 16 in which steps (p) and (q) are conducted in situ.
18. The process of claim 16 in which the compound having the structural formula (12) has the stereochemistry illustrated by the compound having structural formula (12-a)
Figure imgf000062_0001
(12-a), the compound having the structural formula (13) has the stereochemistry illustrated by a compound having structural formula (13-a)
Figure imgf000062_0002
(13-a), and the compound having the structural formula (15) has the stereochemistry illustrated by a compound having structur
Figure imgf000062_0003
(15-a).
19. The process of claim 16 in which the compound having structural formula (12) is substantially pure, enantiomerically enriched
(25)-2-methoxy-2-methyl- 1 -pentanol; the compound having structural formula (13) is substantially pure, enantiomerically enriched
(25)-2-methoxy-2-methylpentanal; and the compound having structural formula (15) is substantially pure, enantiomerically enriched
(lE,25)-2-methoxy-2-methylpentanal 5-tritylthioxime.
20. A process for making substantially pure (±)-tert-butyl-4-hydroxy-2-oxo- pyrrolidinecarboxylate comprising, in toto, the steps of:
(r) reacting (±)-4-amino-3-hydroxy-«-butyric acid, a silating agent, and a third base to provide (±)-4-trimethylsilyloxy-2-oxo-pyπolidine;
(s) reacting the (±)-4-trimethylsilyloxy-2-oxo-pyrrolidine and a tert-butylcarbonyloxy- introducing agent, the third base, and 4-dimethylammopyridine to provide, (±)-tert-butyl-4-trimethylsilyloxy-2-oxo-pyrrolidinecarboxylate;
(t) reacting the (±)-tert-butyl-4-trimethylsilyloxy-2-oxo-pyrrolidinecarboxylate and a desilylating agent to provide (±)-tert-butyl-4-hydroxy-2-oxo-pyπolidinecarboxylate;
and (u) isolating the substantially pure (±)-tert-butyl-4-hydroxy-2-oxo-pyrrolidine- carboxylate.
21. The process of claim 20 in which steps (r), (s), (t), and (u) are conducted sequentially.
22. A process for making a compound having structural formula (19-a)
Figure imgf000063_0001
(19-a), having the absolute stereochemistry illustrated therein, in which the substituents at the carbons labeled "1" and "2" are erythro relative to each other and "and-" relative to the O-R group at the carbon labeled
"3," and in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2 .
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; 4 R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl);
L1 is N(R7), O, S, S(O), or SO2;
R is aryl, furanyl, or thienyl, in which the aryl, the furanyl, and the thienyl are unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and η .
R is hydrogen, alkyl, aryl, or jαr -toluenesulfonyl, comprising, in toto, the steps of:
(v) reacting (±)-tert-butyl-4-hydroxy-2-oxo-pyrrolidinecarboxylate, a fourth base, and a compound having formula (16) X1-SO2-R9
(16),
9 in which R is alkyl, haloalkyl, and aarryyll,, m which the aryl is unsubstituted or substituted with one, two, or three substituents independently selected from the group consisting of alkyl, alkoxy, halo, and nitro; and
X1 is Br r,, CCll,, oorr OOSSOO22--RR99,, to provide tert-butyl 2-oxo-3-pyπoline carboxylate;
(w) reacting the tert-butyl 2-oxo-3-pyπoline carboxylate, a fifth base, and a compound having formula (17) (R0)3SiOSθ2CF3
(17), in which each R is independently selected from the group consisting of alkyl and unsubstituted aryl, to provide a compound having structural formula (18)
Figure imgf000064_0001
(18);
(x) reacting the product of step (w), a second acid, and a substantially enantiomerically enriched compound having structural formula (15-a)
Figure imgf000065_0001
(15-a) to provide a mixture comprising the compound having structural formula (19-a) in equilibrium with a compound having structural formula (19-b)
Figure imgf000065_0002
(19-b), in which the substituents at the carbons labeled "1" and "2" are also erythro
4 relative to each other but are "syn-" relative to the O-R group at the carbon labeled "3," and in which the (19-a)/(19-b) ratio in the mixture is about 4.3: 1 to about 10: 1 ;
(y) allowing the mixture of the compound having structural formula (19-a) and the compound having structural formula (19-b) to further equilibrate until the (19-a)/(19-b) ratio in the mixture is greater than 10: 1;
and
(z) isolating the compound having structural formula (19-a).
23. The process of claim 22 in which steps (v) and (w) are conducted in situ.
24. The process of claim 22 in which steps (x) and (y) are conducted sequentially.
25. The process of claim 22 in which the compound having structural formula (15-a) is substantially pure, substantially enantiomerically enriched
(lE,25)-2-methoxy-2-methylpentanal 5-tritylthioxime; the compound having structural formula (17) is substantially pure tert-butyldimethylsilyl trifluoromethanesulfonate; the compound having structural formula (18) is substantially pure tert-butyl 2-((tert-butyl(dimethyl)silyl)oxy)- 1 H-pyπole- 1 -carboxylate; the compound having structural formula (19-a) is substantially pure, diastereomerically enriched tert-butyl (2R)-2-((lR,25)-2-methoxy-2-methyl-l-((tritylsulfanyl)amino)pentyl)-5-oxo-
2,5-dihydro- 1 - 1 H-pyrrole- 1 -carboxylate; and the compound having structural formula (19-b) is substantially pure, diastereomerically enriched tert-butyl (25)-2-(( 15,25)-2-methoxy-2-methyl- 1 - ((tritylsulfanyl)amino)pentyl)-5-oxo-2,5-dihydro-l-lH-pyπole-l-carboxylate.
26. A process for ctural formula (24)
Figure imgf000066_0001
(24) in which the carbon-carbon double bond is substantially in the Z configuration, and in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl); and R is methyl, ethyl, zsø-propyl, or vinyl, comprising, in toto, the steps of: (aa) reacting a compound having structural formula (19)
Figure imgf000066_0002
(19), a conjugate addition agent said conjugate addition agent comprising a mixture of compounds having structural formula (20-Z)
Figure imgf000066_0003
(20-Z) and structural formula (20-E)
Figure imgf000067_0001
(20-E), in which the (20-Z)/(20-E) ratio in the mixture is about 97:3, and in which Q is Li, Mg-Cl, Mg-Br, or Mg-I, and, optionally, a second additive at a temperature between about -50 °C and about -30 °C about to provide a compound having structural formula (21)
Figure imgf000067_0002
(21) in which the carbon-carbon double bond is substantially in the Z configuration; (bb) reacting the product of step (aa) and a third acid to provide a compound having the structural formula (22)
Figure imgf000067_0003
or a salt thereof;
(cc) reacting the product of step (bb), an acetylating agent, and a sixth base to provide a compound having the structural formula (23)
Figure imgf000067_0004
(23);
(dd) reacting the product of step (cc), a tert-butylcarbonyloxy-introducing agent, a seventh base, and 4-dimethylaminopyridine to provide the compound having formula (24);
and
(ee) optionally isolating the product of step (dd).
27. The process of claim 26 in which steps (aa)-(dd) are conducted in situ.
28. The process of claim 26 in which the compound having the structural formula (19) has the absolute stereochemistry illustrated by a compound having structural formula (19-a)
Figure imgf000068_0001
(19-a), the compound having the structural formula (21) has the absolute stereochemistry illustrated by a compound
Figure imgf000068_0002
(21-a), the compound having the structural formula (22) has the absolute stereochemistry illustrated by a compound having structural formula (22-a)
Figure imgf000069_0001
(22-a), the compound having the structural formula (23) has the absolute stereochemistry illustrated by a compound having structural formula (23 -a)
Figure imgf000069_0002
(23-a), and the compound having the structural formula (24) has the absolute stereochemistry illustrated by a compound hav
Figure imgf000069_0003
(24-a).
29. The process of claim 26 in which the compound having structural formula (19) is substantially pure, diastereomerically enriched tert-butyl (2R)-2-((lR,25)-2-methoxy-2-methyl-l-((tritylsulfanyl)amino)pentyl)-5-oxo-2,
5 -dihydro- 1-1 H-pyπole- 1 -carboxylate; the compound having structural formula (21) is substantially pure, substantially diastereomerically enriched tert-butyl (2R,35)-2-((lR,25)-2-methoxy-2-methyl-l-((tritylsulfanyl)amino)pentyl)-5- oxo-3 -(( 1 )- 1 -propenyl)- 1 -pyπolidinecarboxylate; the compound having structural formula (22) is substantially pure, substantially diastereomerically enriched
(45,5R)-5-((lR,25)-l-amino-2-methoxy-2-methylpentyl)-4-((lZ)-l-propenyl)-2- pyπolidinone; the compound having structural formula (23) is substantially pure, substantially diastereomerically enriched N-((lR,25)-2-methoxy-2-methyl-l-((2R,35)-5-oxo-3-((lZ)-l- propenyl)pyπolidinyl)pentyl)acetamide; and the compound having structural formula (24) is substantially pure, substantially diastereomerically enriched tert-butyl (2R,3S)-2-((lR,2S)- 1 -(acetylamino)-2-methoxy-2-methylpentyl)-5-oxo-3-((lZ)- 1 -propenyl)- 1 -pyrrolidinecarboxylate .
30. A process for making a compound having structural formula (28)
Figure imgf000070_0001
(28), or a therapeutically acceptable salt thereof, in which R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl; R is alkyl, cycloalkyalkyl, or aryl-(C2-C -alkyl); R is methyl, ethyl, iso-propyl, or vinyl; and
12
R is hydrogen or alkyl, comprising, in toto, the steps of:
(ff) reacting a compound having structural formula (24)
Figure imgf000070_0002
(24) and a fourth reducing agent to provide a compound having structural formula (25)
Figure imgf000071_0001
(25);
(gg) optionally reacting the product of step (ff), a -C5 alcohol, a trialkylorthoformate, and a second acid catalyst to formula (26)
Figure imgf000071_0002
(26), in which R is methyl, ethyl, propyl, or z'sø-propyl;
(hh) reacting the product of step (ff) or step (gg), a cyanide-donating agent, and a fourth acid to provide a compound having structural formula 27
Figure imgf000071_0003
(27);
(ii) reacting the product of step (hh), a -C5 alcohol, and a fifth acid to provide the compound having structural formula (28), or a therapeutically acceptable salt thereof;
and
(jj) isolating the product of step (ii).
31. The process of claim 30 in which steps (ff), (gg), (hh), and (ii) are conducted in situ.
32. The process of claim 30 in which the compound having the structural formula (24) has the absolute stereochemistry illustrated by a compound having structural formula (24-a)
Figure imgf000072_0001
(24-a), the compound having the structural formula (25) has the absolute stereochemistry illustrated by a compound having structural formula (25 -a)
Figure imgf000072_0002
(25-a), the compound having the structural formula (26) has the absolute stereochemistry illustrated by a compound having structural formula (26-a)
Figure imgf000072_0003
(26-a), the compound having the structural formula (27) has the absolute stereochemistry illustrated by a compound having structural formula (27-a)
Figure imgf000073_0001
(27-a), and the compound having the structural formula (28) has the absolute stereochemistry illustrated by a compound
Figure imgf000073_0002
(28-a).
33. The process of claim 30 in which the compound having structural formula (24) is substantially pure, diastereomerically enriched tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-oxo-3-((lZ)-
1 -propenyl)- 1 -pyrrolidinecarboxylate; the compound having structural formula (25) is substantially pure, diastereomerically enriched 2: 1 anomeric tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-
5 -hydroxy-3 -(( 1 Z)- 1 -propenyl)- 1 -pyrrolidinecarboxylate ; the compound having structural formula (26) is substantially pure, diastereomerically enriched tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-methoxy-3- (( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate; the compound having structural formula (27) is substantially pure, diastereomerically enriched tert-butyl (2R,35,5R)-2-((lR,25)-l -(acetylamino)-2-methoxy-2-methylpentyl)-5-cyano-3-
(( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate; and the compound having structural formula (28) is substantially pure, diastereomerically enriched isopropyl (2R,5R)-5-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-4-((lZ)-l- propenyl-2 -pyrrolidinecarboxylate, /jαrα-toluenesulfonic acid salt.
34. A compound selected from the group consisting of a compound having structural formula (29)
a compound having structural
Figure imgf000074_0001
(29-a),
a compound having structural formula (30)
and a compound having
Figure imgf000074_0002
(30-a), or a salt thereof, in which the carbon-carbon double bond in the compounds having structural formulas (29), (29-a), (30), and (30-a) is substantially in the Z configuration, and in which
R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
2 R is alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl;
4 R is alkyl, cycloalkyalkyl, or aryl-(C2-C4-alkyl);
R is methyl, ethyl, isø-propyl, or vinyl;
13
R is alkoxy alkoxycarbonyl, and hydroxy; R is hydrogen or tert-butoxycarbonyl; and R is hydrogen or acetyl,
13 with the proviso that R is alkoxycarbonyl only for the compound having structural formula (30-a).
35. A compound of claim 34 having structural formula (29) in which R is alkyl; R is alkyl; R is alkyl; R is hydrogen, and R is hydrogen.
36. A compound of claim 35 which is
(4S,5R)-5-((\R,2S)- 1 -amino-2-methoxy-2-methylpentyl)-4-((l Z)- 1 -propenyl)-2- pyπolidinone.
37. A compound of claim 34 having structural formula (29) in which R is alkyl; R is alkyl; R is alkyl; R is hydrogen, and R is acetyl.
38. A compound of claim 37 which is N-((lR,25)-2-methoxy-2-methyl-l-((2R,35)-5-oxo-3-((lZ)-l-propenyl)pyrrolidinyl)- pentyl)acetamide .
39. A compound of claim 34 having structural formula (29) in which R is
2 4 14 15 alkyl; R is alkyl; R is alkyl; R is tert-butoxycarbonyl, and R is acetyl.
40. A compound of claim 39 which is tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-oxo-3-((lZ)- 1 -propenyl)- 1 -pyπolidinecarboxylate.
41. A compound of claim 34 having structural formula (30) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxy; R is tert-butoxycarbonyl, and R is acetyl.
42. A compound of claim 41 which is anomeric tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5- hydroxy-3 -(( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate.
43. A compound of claim 34 having structural formula (30) in which R is alkyl; R is alkyl; R is alkyl; R is hydroxy; R is tert-butoxycarbonyl, and R is acetyl.
44. A compound of claim 43 which is tert-butyl (2R,35)-2-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-5-methoxy-3- (( 1 Z)- 1 -propenyl)- 1 -pyπolidinecarboxylate.
45. A compound of claim 34 having structural formula (30-a) in which R is alkyl; R is alkyl; R is alkyl; R is alkoxycarbonyl; R is hydrogen, and R is acetyl.
46. A compound of claim 45 which is isopropyl (2R,5R)-5-((lR,25)-l-(acetylamino)-2-methoxy-2-methylpentyl)-4-((lZ)-l- propenyl)-2 -pyπolidinecarboxylate, pαra-toluenesulfonic acid salt.
PCT/US2002/008074 2001-04-03 2002-03-18 Process for the preparation of substituted pyrrolidine neuraminidase inhibitors WO2002081441A1 (en)

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