Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D205/00—Heterocyclic compounds containing four-membered rings with one nitrogen atom as the only ring hetero atom
  • C07D205/02—Heterocyclic compounds containing four-membered rings with one nitrogen atom as the only ring hetero atom not condensed with other rings
  • C07D205/06—Heterocyclic compounds containing four-membered rings with one nitrogen atom as the only ring hetero atom not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member
  • C07D205/08—Heterocyclic compounds containing four-membered rings with one nitrogen atom as the only ring hetero atom not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with one oxygen atom directly attached in position 2, e.g. beta-lactams
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
  • C07F7/1804—Compounds having Si-O-C linkages
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
  • C07F7/1804—Compounds having Si-O-C linkages
  • C07F7/1872—Preparation; Treatments not provided for in C07F7/20
  • C07F7/1892—Preparation; Treatments not provided for in C07F7/20 by reactions not provided for in C07F7/1876 - C07F7/1888
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/55—Design of synthesis routes, e.g. reducing the use of auxiliary or protecting groups

Definitions

• This invention relates to an enantioselective process for producing hydroxy-alkyl substituted azetidinones useful as hypocholesterolemic agents, in particular for preparing 1-(4-fluorophenyl)-3(R)-[3(S)-hydroxy-3- (4-fluorophenyl)propyl)]-4(S)-(4-hydroxyphenyl)-2-azetidinone, claimed in US 5,767,115. Processes for preparing the corresponding azetidinone without the
• This invention provides an improved simple, high-yielding process using neutral conditions for producing the hypocholesterolemic azetidinone having the formula I
• the process of this invention is a high throughput process which provides the desired azetidinone in high overall yield in a short time cycle (i.e., about two weeks).
• TEA is triethylamine
• DMAP is 4-dimethyl- amino pyridine
• DIPEA is diisopropylethylamine
• BSA is bistrimethylsilyl acetamide
• TBAF is tetra n-butyl-ammonium fluoride
• t-BuOMe is t-butyl methyl ether
• Prot is a silyl protecting group as defined below.
• step (b) for reducing a ketone to a hydroxy group using a borane reducing agent such as BH3* S(CH3)2 in the presence of a chiral catalyst such as (R)-tetrahydro-1-methyl-3,3-diphenyl- 1 H,3H-pyrrolo(1 ,2-c)(1 ,3,2) oxaza-borolidine is known: see U.S. 5,767,115.
• step (c) the chiral alcohol, V, and the imine, VI, are protected with a suitable hydroxy-protecting group, preferably a silyl protecting group such as that derived from chlorotrimethylsilane (TMSCI) or t-butyldimethyl-silyl chloride (TBDMSCI).
• TMSCI chlorotrimethylsilane
• TDMMSCI t-butyldimethyl-silyl chloride
• the alcohol (1 equivalent) and imine (preferaby 1-3 equivalents) are added to an anhydrous solvent such as CH2CI2, the reaction mixture is cooled to -10° to 15°C, a tertiary amine base such as DIPEA is added (preferably 2-4 equivalents), and sufficient silylating reagent to react with both the alcohol and the imine is added (e.g., 2-4 equivalents).
• the alcohol and imine are condensed by reacting at -20° to -35°C with at least 1 equivalent of a Lewis acid such as TiCU, in the presence of a tertiary amine base (preferably 1-3 equivalents) such as DIPEA for 2-4 hours.
• a Lewis acid such as TiCU
• a tertiary amine base preferably 1-3 equivalents
• DIPEA tertiary amine base
• the reaction is quenched, for example by treating with an acid such as glacial acetic acid followed by aqueous tartaric acid solution; the resultant product is extracted and crystallized using conventional procedures.
• Silylation in step (d) is effected by reacting the compound of formula VII with a silyl-enol ether silylating agent such as bistrimethylsilyl acetamide (BSA), N-methyl-O-trimethylsilyl acetamide or iso-propenyloxy trimethylsilane, preferably BSA, in a suitable inert organic solvent at -20°C to 110°C, preferably at about 0°C to 25°C.
• BSA bistrimethylsilyl acetamide
• N-methyl-O-trimethylsilyl acetamide or iso-propenyloxy trimethylsilane preferably BSA
• the reaction is preferably carried out in a dry, inert atmosphere, e.g., the solvent is dried, typically with molecular sieves, and the reaction is carried out under nitrogen.
• the ⁇ -(substituted-amino)amide can first be reacted with the silylating agent and then reacted with the cyclizing agent, or the compound of formula VII can be added to a mixture of the silylating agent and the cyclizing agent.
• the silylation and cyclization are done sequentially, i.e., the silylating agent is reacted with the starting material first, the silylation reaction can be allowed to continue for up to about two hours, but preferably the cyclization step is carried out immediately after silylation, or the silylating agent and the cyclizing agent are added simultaneously.
• the source of the fluoride ion used to catalyze the intra-molecular cyclization of the compound of formula VII is typically a quaternary alkyl-, aryl-alkyl- or arylalkyl-alkylammonium fluoride salt or a hydrate thereof, or a mixture thereof, or is an alkali metal fluoride salt or a hydrate thereof, such as cesium fluoride or potassium fluoride.
• arylalkyl- alkylammonium groups are benzyltriethyl-ammonium and benzyltrimethyl- ammonium; examples of arylalkyl-ammonium are phenyltriethyl- ammonium and phenyltrimethyl-ammonium; typical alkylammonium groups contain alkyl groups of 1-6 carbon atoms, e.g., tetra n-butyl-ammonium.
• the reagent is added in a catalytic amount, i.e., about 0.1 to about 20 mole percent, preferably about 0.5 to 5 mole percent, and when an anhydrous quaternary ammonium fluoride salt is used, it can be added in a catalytic up to a stoichiometric amount.
• a catalytic amount i.e., about 0.1 to about 20 mole percent, preferably about 0.5 to 5 mole percent
• an anhydrous quaternary ammonium fluoride salt it can be added in a catalytic up to a stoichiometric amount.
• an alkali metal fluoride salt it is added in catalytic amount up to a stoichiometric amount compared to the starting ⁇ -amino compound, depending on the solubility of the reagent in the solvent used (higher solubility requires less reagent).
• the fluoride reagent is added directly to the reaction mixture resulting from silylation, and is reacted at about 0°C to 110°C, preferably about 0°C to 50°C, for about 0.5 to about 6 hours, preferably about 2 hours.
• a preferred fluoride ion catalyst cyclizing agent is tetrabutylammonium fluoride trihydrate.
• the cyclization of step (d) can be effected by the addition of a monovalent quaternary ammonium salt of the chiral auxiliary of formula III used in step (a), i.e., a compound of the formula
• X, Yand R 1 are as defined above and Z is a quaternary ammonium cation selected from the group consisting of arylalkyl-alkylammonium, aryl- alkylammonium and tetraalkylammonium, or a mixture thereof, and alkali metals.
• arylalkyl-alkylammonium examples include benzyltriethylammonium and benzyl-trimethylammonium; examples of aryl-alkylammonium are phenyltriethylammonium and phenyltrimethyl-ammonium; typical tetraalkylammonium groups contain alkyl groups of 1-6 carbon atoms, e.g., tetra n-butylammonium; and typical alkali metals are sodium, potassium, cesium and lithium.
• chiral or non-chiral auxiliaries can also be used to cyclize the ⁇ -(substituted-amino)amide of formula VII, for example compounds of the formulas wherein X, Y, Z and R 1 are as defined above and R 2 is defined as for R 1 can also be used.
• the the ⁇ -(substituted-amino)amide of formula VII is treated with a silylating agent as described above, with the salt of the chiral (or non-chiral) auxiliary being added either simultaneously or sequentially in a catalytic or stoichiometric amount compared to the ⁇ -amino compound under conditions similar to the reaction with fluoride ion.
• a third method for cyclizing the ⁇ -(substituted-amino)amide of formula VII comprises using a strong non-nucleophilic base.
• a strong non- nucleophilic base is defined herein as a non-aqueous base which does not act as a nucleopile by virtue of its steric bulk, e.g., sodium bistrimethylsilylamide or lithium diisopropylamide.
• the base is reacted with the the ⁇ -amino compound in an inert organic solvent such as CH 2 CI 2 at a temperature of about -100°C to 10 °C. Removal of the protecting groups after cyclization is carried out using conventional methods, for example by treatment with a dilute acid such as sulfuric acid in a solvent such as an alcohol, e.g., isopropanol.
• the azetidinone resulting from the cyclization can be purified by appropriate standard procedures such as crystallization or column chromatography.
• suitable inert organic solvent means any organic solvent or combination of solvents that is unreactive in the reaction being conducted and is a solvent for the reactants.
• suitable solvents are halogenated compounds such as CH2CI2; heterocyclic compounds such as tetrahydrofuran (THF); DMSO; dimethylformamide (DMF); acetonitrile; carbocyclic aromatics such as toluene; and t-BuOMe.
• halogenated compounds such as CH2CI2
• heterocyclic compounds such as tetrahydrofuran (THF); DMSO; dimethylformamide (DMF); acetonitrile; carbocyclic aromatics such as toluene; and t-BuOMe.
• THF tetrahydrofuran
• DMSO dimethylformamide
• acetonitrile carbocyclic aromatics
• carbocyclic aromatics such as toluene
• t-BuOMe Preferred are t-BuOMe,
• step (d) for cyclization of step (d) to proceed as desired, the -OH substituents present in the intermediates of formulas V and VI used in step (c) must be protected prior to cyclization, hence the treatment in step (c) with a hydroxy-protecting group.
• a key feature of this process is the surprising stability of the silyl protecting groups on the carbinol and phenol moieties in both step (c) and step (d).
• step (c) after the reaction of intermediates V and VI, the reaction is quenched with acid, preferably acetic acid and aqueous tartaric acid: the resulting solution has a pH ⁇ 1.
• acid preferably acetic acid and aqueous tartaric acid: the resulting solution has a pH ⁇ 1.
• step (d) of the process of the invention out of the three silylated groups (i.e., the two hydroxy groups silylated in step (c) and the -NH- group silylated in the first part of step (d)), the -N-Si- group is selectively desilylated, allowing the intramolecular cyclization to proceed efficiently. This was unpredictable, especially in view of the presence of a silylated phenol group.
• Step fe Add a premixed solution of isopropyl alcohol (250 mL) and 2N H 2 S0 4 (25 mL) to the product of step (d) and agitate the mixture at room temperature for 1 h. Crystallize compound I from aqueous isopropyl alcohol. Filter the product and wash with dilute aqueous isopropyl alcohol followed by water until the pH of wash is ⁇ 5. Dry the product at 60°C in a draft oven or under vacuum to give 26.14 g (91.5% molar yield) of compound I.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
• Plural Heterocyclic Compounds (AREA)
• Heterocyclic Carbon Compounds Containing A Hetero Ring Having Nitrogen And Oxygen As The Only Ring Hetero Atoms (AREA)
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Citations (5)

• 1999
  • 1999-12-06 EP EP99963973A patent/EP1137634B1/en not_active Expired - Lifetime
  • 1999-12-06 CN CN99814140A patent/CN1130342C/zh not_active Expired - Lifetime
  • 1999-12-06 AR ARP990106206A patent/AR025144A1/es not_active Application Discontinuation
  • 1999-12-06 CA CA002353981A patent/CA2353981C/en not_active Expired - Fee Related
  • 1999-12-06 HK HK02100567.1A patent/HK1039487B/en not_active IP Right Cessation
  • 1999-12-06 JP JP2000586688A patent/JP3640888B2/ja not_active Expired - Lifetime
  • 1999-12-06 PT PT99963973T patent/PT1137634E/pt unknown
  • 1999-12-06 DE DE69925862T patent/DE69925862T2/de not_active Expired - Lifetime
  • 1999-12-06 WO PCT/US1999/027914 patent/WO2000034240A1/en not_active Ceased
  • 1999-12-06 AU AU20301/00A patent/AU2030100A/en not_active Abandoned
  • 1999-12-06 ES ES99963973T patent/ES2244238T3/es not_active Expired - Lifetime
  • 1999-12-06 AT AT99963973T patent/ATE297892T1/de active
• 2001
  • 2001-05-16 ZA ZA200104004A patent/ZA200104004B/en unknown
• 2004
  • 2004-11-09 JP JP2004325744A patent/JP4616620B2/ja not_active Expired - Lifetime
• 2010
  • 2010-09-27 JP JP2010216153A patent/JP2011016841A/ja not_active Withdrawn

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