Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D487/00—Heterocyclic compounds containing nitrogen atoms as the only ring hetero atoms in the condensed system, not provided for by groups C07D451/00 - C07D477/00
  • C07D487/02—Heterocyclic compounds containing nitrogen atoms as the only ring hetero atoms in the condensed system, not provided for by groups C07D451/00 - C07D477/00 in which the condensed system contains two hetero rings
  • C07D487/04—Ortho-condensed systems
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/495—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with two or more nitrogen atoms as the only ring heteroatoms, e.g. piperazine or tetrazines
  • A61K31/4985—Pyrazines or piperazines ortho- or peri-condensed with heterocyclic ring systems
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P3/00—Drugs for disorders of the metabolism
  • A61P3/08—Drugs for disorders of the metabolism for glucose homeostasis
  • A61P3/10—Drugs for disorders of the metabolism for glucose homeostasis for hyperglycaemia, e.g. antidiabetics

Definitions

• aspects of the present application relate to processes for the preparation of sitagliptin and pharmaceutically acceptable salts thereof.
• the drug compound having the adopted name "sitagliptin phosphate” has chemical names: 7-[(3R)-3-amino-1 -oxo-4-(2,4,5-trifluorophenyl)butyl]-5,6,7,8- tetrahydro-3-(thfluoromethyl)-1 ,2,4-thazolo[4,3-a]pyrazine phosphate (1 :1 ); or (2R)-4-oxo-4-[3-(thfluoromethyl) -5,6-dihydro[1 ,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]- 1 -(2,4,5-thfluorophenyl)butan-2-amine phosphate; and is represented by structural Formula I.
• Sitagliptin is a glucagon like peptide 1 metabolism modulator, hypoglycemic agent and dipeptidyl peptidase IV inhibitor, and is believed to exert its action in patients with type 2 diabetes by slowing the inactivation of incretin hormones.
• An oral tablet product containing sitagliptin phosphate monohydrate as the active ingredient is marketed in the United States by Merck & Co., Inc. using the brand JANUVIATM. JANUVIA is indicated to improve glycemic control in patients with type 2 diabetes mellitus.
• Sitagliptin phosphate monohydrate, in combination with metformin hydrochloride, is sold by Merck & Co., Inc. using the brand JANUMETTM in the form of tablets for oral administration, for combination therapy in the treatment of type 2 diabetes.
• U.S. Patent No. 6,699,871 describes various DPP-IV inhibitors including sitagliptin and their pharmaceutically acceptable salts, a pharmaceutical composition and method of treatment and a process for the preparation of sitagliptin hydrochloride.
• International Application Publication No. WO 2004/085661 A2 discloses a process for the preparation of sitagliptin, in which (S)-phenylglycine amide is used as a chiral auxilary to form an intermediate, which subsequently provides the desired enantiomer (sitagliptin).
• stereoselective processes for the preparation of sitagliptin of Formula II, or a salt thereof, as a single enantiomer or in an enantiomerically enriched form comprising:
• R is Ci-C 4 alkyl and Ph is phenyl, to afford a compound of Formula V;
• Ph is a phenyl group
• compositions that include sitagliptin or its pharmaceutically acceptable salt or anhydrate and at least one pharmaceutically acceptable excipient.
• Fig. 1 is an illustration of a powder X-ray diffraction (PXRD) pattern of crystalline 7-[1 -oxo-(3R)-(R-1 -phenylethylamino)-4(2,4,5-trifluorophenyl)-butyl)-3- trifluoromethyl-5,6,7,8-tetrahydro-1 ,2,4-triazoleo[4,3-a]pyrazine hydrochloride, prepared according to Example 5.
• PXRD powder X-ray diffraction
• Fig. 2 is an illustration of a thermogravimetric analysis (TGA) curve of crystalline 7-[1 -oxo-(3R)-(R-1 -phenylethylamino)-4(2,4,5-trifluorophenyl)-butyl)-3- trifluoromethyl-5,6,7,8-tetrahydro-1 ,2,4-triazoleo[4,3-a]pyrazine hydrochloride, prepared according to Example 5.
• TGA thermogravimetric analysis
• Fig. 3 is an illustration of a PXRD pattern of a crystalline dihydrogen phosphate salt of sitagliptin, prepared according to Example 9.
• pure When a molecule or other material is identified herein as “pure”, it generally means, unless specified otherwise, that the material has 99% purity or higher, as determined using methods conventional in the art such as high performance liquid chromatography (HPLC), gas chromatography (GC), or spectroscopic methods. In general, this refers to purity with regard to unwanted residual solvents, reaction by-products, impurities, and unreacted starting materials. In the case of stereoisomers, “pure” also means 99% of one enantiomer or diastereomer, as appropriate. “Substantially pure” refers to the same as “pure,” except that the lower limit is about 98% purity or higher and, likewise, “essentially pure” means the same as “pure” except that the lower limit is about 97% purity.
• % enantiomeric excess (abbreviated “ee) shall mean the percentage of major enantiomer less the percentage of minor enantiomer. Thus, a 70% enantiomeric excess corresponds to formation of 85% of one enantiomer and 15% of the other.
• enantiomeric excess is synonymous with the term “optical purity.”
• the processes of the present invention provide a compound of structural Formula I with high optical purity, typically in excess of 80% ee.
• a compound of Formula I is obtained with an optical purity in excess of 90% ee.
• a compound of Formula I is obtained with an optical purity in excess of 95% ee. In embodiments, a compound of Formula I is obtained with an optical purity in excess of 97% ee.
• the present patent application provides stereoselective processes for the preparation of sitagliptin of Formula II, or a salt thereof, as a single enantiomer or in an enantiomehcally enriched form, each step of which is separately contemplated.
• Embodiments of processes include the steps:
• R is Ci-C 4 alkyl and Ph is phenyl, to afford a compound of Formula V;
• HY is an acid moiety
• Step (i) involves preparing an enamide of structural Formula V containing a (R)-(+)-1 -phenylalkylamine, such as (R)-(+)-1 -phenylethylamine, as a chiral auxiliary.
• the quantity of (R)-1 -phenylalkylamine may range from about 1 to about 2 molar equivalents, per mole of the compound of Formula III.
• Suitable solvents include, but are not limited to: alcohols such as methanol, ethanol, isopropyl alcohol, and n-butanol; halogenated hydrocarbons such as dichloromethane, ethylene dichloride, and chloroform;
• esters such as ethyl acetate, n-propyl acetate, and isopropyl acetate
• hydrocarbons such as toluene, xylene, n-hexane, n-heptane, and cyclohexane; ethers such as 1 ,4-dioxane and tetrahydrofuran; organic acids such as acetic acid, propionic acid, and the like; and any mixtures thereof.
• the reaction may be carried out in the absence of a solvent.
• Suitable temperatures for the reaction of step (i) may be less than about 150 0 C, less than about 120 0 C, less than about 80°C, less than about 60 0 C, or any other suitable temperatures.
• Suitable times for the reaction of step (i) may be from about 30 minutes to about 10 hours, or longer.
• Step (ii) involves converting a compound of Formula V to a compound of Formula Vl or its salt.
• Step (ii) of the present application includes a diastereoselective reduction of the enamine carbon-carbon double bond in the chiral substrate of Formula V, to afford a protected chiral amine of Formula Vl.
• the diastereoselective reduction may be carried out in the presence of a borohydhde such as sodium borohydride, sodium cyanoborohydride, lithium borohydride, and the like, and a sulfonic acid such as methanesulfonic acid, p-toluenesulfonic, acid and the like.
• the quantities of sodium borohydride may range from about 1 to about 10 molar equivalents, per mole of the compound of Formula V.
• the quantities of sulfonic acid may range from about 1 to about 10 molar equivalents, per mole of the compound of Formula V.
• Solvents that may be used in step (ii) include, but are not limited to:
• alcohols such as methanol, ethanol, isopropyl alcohol, hexafluoroisopropyl alcohol, phenol, 2,2,2-trifluoroethanol (TFE), and the like; halogenated
• hydrocarbons such as dichloromethane, ethylene dichloride, and chloroform
• hydrocarbons such as toluene, xylene, n-hexane, n-heptane, and cyclohexane
• ethers such as 1 ,4-dioxane, tetrahydrofuran, and methyl t-butyl ether
• aprotic polar solvents such as N,N-dimethylfornnannide (DMF), dimethylsulfoxide (DMSO), and dimethylacetamide (DMA); and any mixtures thereof.
• the reaction may be carried out without a solvent.
• Suitable temperatures for the reaction may be less than about 150 0 C, less than about 100 0 C, less than about 60°C, less than about 25°C, less than about 0 0 C, less than about -25°C, less than about -50 0 C, or any other suitable temperatures.
• the reaction may be carried out for time periods ranging from about 30 minutes to about 10 hours, or longer.
• the compound of Formula Vl or its salt can further be purified by a process involving acidifying and basifying steps, in any order, crystallization, and combinations thereof, to enhance the diastereomehc ratio.
• crystallization techniques include, but are not limited to: concentrating, cooling, stirring, or shaking a solution containing the compound, combining a solution with an anti-solvent, adding seed crystals, evaporation, flash evaporation, and the like, including any combinations thereof.
• the solvents that can be employed for crystallization include, but are not limited to: alcohols, such as methanol, ethanol, isopropyl alcohol, hexafluoroisopropyl alcohol, phenol, and 2,2,2-trifluoroethanol (TFE); esters such as ethyl acetate, n-propyl acetate, and isopropyl acetate;
• ketones such as acetone and methyl isobutyl ketone
• hydrocarbons such as toluene and xylene
• halogenated hydrocarbons such as dichloromethane and chloroform
• ethers such as 1 ,4-dioxane and tetrahydrofuran
• nitriles such as acetonitrile
• water and any mixtures thereof.
• An anti-solvent as used herein refers to a solvent in which a compound of Formula Vl is insoluble, less soluble, or poorly soluble.
• Acids that can be employed for purification include, but are not limited to: inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and the like; and organic acids such as acetic acid, methanesulfonic acid, oxalic acid, formic acid, and the like.
• Bases that can be employed for purification include, but are not limited to: inorganic bases such as alkali metal hydroxides and carbonates; and organic bases such as thethylamine, dicyclohexylamine, diisopropylethylamine, morpholine, ammonium hydroxide, and the like.
• the compound of Formula Vl or its salt has a diastereomeric ratio of more than 80:20, or more than 95:5, or about 100:0.
• Step (iii) in the process of the present application entails the removal of (R)- 1 -phenylalkylamine under hydrogenolytic conditions to afford sitagliptin free base of Formula Il or its salt, as a single enantiomer or in an enantiomerically enriched form, which, if desired, can further be converted to an acid addition salt of sitagliptin of Formula VII by reacting sitagliptin of Formula Il with a suitable acid.
• the removal of the (R)-(+)-1-phenylalkylamine may be achieved by techniques known in the art. For example, it may be achieved by catalytic hydrogenation in the presence of a catalyst such as, for example, palladium on carbon, Raney nickel, and palladium hydroxide on carbon, or by transfer hydrogenation using ammonium formate, hydrazine, formic acid, and the like as a source of hydrogen.
• a catalyst such as, for example, palladium on carbon, Raney nickel, and palladium hydroxide on carbon
• transfer hydrogenation using ammonium formate, hydrazine, formic acid, and the like as a source of hydrogen.
• Solvents that may be used for hydrogenation include, but are not limited to: alcohols such as methanol, ethanol, isopropyl alcohol, and n-butanol; halogenated hydrocarbons such as dichloromethane, ethylene dichloride, and chloroform;
• esters such as ethyl acetate, n-propyl acetate, and isopropyl acetate
• hydrocarbons such as toluene, xylene, n-hexane, n-heptane, and cyclohexane; ethers such as 1 ,4-dioxane and tetrahydrofuran; aprotic polar solvents such as N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMA); water; and any mixtures thereof.
• the reaction may be carried without a solvent.
• Suitable temperatures for the reaction may be less than about 150 0 C, less than about 100 0 C, less than about 80°C, less than about 60 0 C, or any other suitable temperatures.
• Suitable times for the hydrogenation step may be from about 30 minutes to about 10 hours, or longer.
• an enantiomerically pure acid addition salt of sitagliptin obtained in the above step is neutralized using a suitable base, for example, an ammonia solution.
• enantiomerically pure sitagliptin free base of Formula Il may be isolated, purified (if desired), and then subsequently converted to an acid addition salt of sitagliptin of Formula VII, by reacting with a suitable acid.
• suitable acids for preparation of an acid addition salt of sitagliptin of Formula VII include, but are not limited to, hydrochloric acid, phosphoric acid, oxalic acid, hydrobromic acid, acetic acid, formic acid, succinic acid, mandelic acid, fumaric acid, benzoic acid, and the like.
• Solvents that may be used for the conversion of enantiomerically pure sitagliptin free base to an acid addition salt of sitagliptin of Formula VII include, but are not limited to: alcohols such as methanol, ethanol, isopropyl alcohol, and n- butanol; halogenated hydrocarbons such as dichloromethane, ethylene dichloride, and chloroform; esters such as ethyl acetate, n-propyl acetate, and isopropyl acetate; hydrocarbons such as toluene, xylene, n-hexane, n-heptane, and cyclohexane; ethers such as 1 ,4-dioxane and tetrahydrofuran; aprotic polar solvents such as N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMA); water; and any mixtures thereof.
• Suitable temperatures for the reaction may be less than about 100 0 C, less than about 80 0 C, less than about 60°C, or any other suitable temperatures.
• Suitable times for the reaction may be from about 30 minutes to about 10 hours, or longer.
• an acid addition salt of sitagliptin may be purified by processes known in the art.
• an acid addition salt of sitagliptin may be purified by precipitation or slurrying in a suitable solvent. The precipitation may be achieved by crystallization, by combining a solution with an anti-solvent, or any other suitable methods known in the art.
• An anti-solvent as used herein refers to a liquid in which a salt of sitagliptin is insoluble or poorly soluble.
• An acid addition salt of sitagliptin prepared in accordance with the processes described in the present application are substantially free of process or structure related impurities.
• “Substantially free” as used herein refers to sitagliptin free base or a pharmaceutically acceptable salt having less than about 0.5%, or less than about 0.3%, or less than about 0.2%, or less than about 0.1 %, or less than about 0.05%, by weight of a corresponding process or structural related impurity.
• Conversion of an acid addition salt of sitagliptin of Formula VII back into sitagliptin free base is also contemplated.
• the compounds at any stage of the process of the present invention may be recovered from a suspension/solution using any of techniques such as decantation, filtration by gravity or by suction, centrifugation, slow evaporation, and the like or any other suitable techniques.
• the solids that are isolated may carry a small proportion of occluded mother liquor containing a higher percentage of impurities. If desired, the solids may be washed with a solvent to wash out the mother liquor and/or impurities and the resulting wet solids may optionally be suction dried.
• Evaporation refers to distilling of solvent almost completely at atmospheric pressure or under reduced pressure. Flash evaporation as used herein refers to distilling of solvent by using a technique including, but not limited to, tray drying, spray drying, fludized bed drying, and thin film drying, under reduced pressure or at atmospheric pressure.
• a wet cake obtained at any stage of the process may be optionally further dried. Drying may be carried out using a tray dryer, vacuum oven, air oven, fluidized bed dryer, spin flash dryer, flash dryer, and the like, at atmospheric pressure or under reduced pressure. Drying may be carried out at temperatures less than about 200 0 C, or about 20 0 C to about 80°C, or about 30 0 C to about 60°C, or any other suitable temperatures, at atmospheric pressure or under reduced pressure. The drying may be carried out for any desired times until the desired quality of product is achieved, such as about 30 minutes to about 20 hours, or about 1 to about 10 hours. Shorter or longer times also are useful.
• the present invention includes one-pot processes, where one or more intermediate compounds are not isolated, for preparing a compound of Formula V, starting from 2,4,5-trifluorophenylacetic acid, embodiments of which comprise at least one of the steps:
• Formula VlIl Formula IX Formula X (ii) reacting the compound of Formula X with 3-thfluoromethyl-5,6,7,8- tetrahydro-1 ,2,4-triazolo[4,3a]pyrazine hydrochloride of Formula Xl, in the presence of diisopropylethylamine, to afford the compound of Formula III; and
• Step (i) involves condensation of 2,4,5-trifluorophenyl acetic acid with 2,2- dimethyl-1 ,3-dioxane-4,6-dione (Meldrums acid) of Formula IX.
• the quantity of Meldrums acid that may be used in step (i) may be less than about 2, or less than about 3, or less than about 5 molar equivalents, per mole of the compound of Formula VIII.
• Bases that may be used in step (i) include, but are not limited to: organic bases, such as, for example, triethylamine, diisopropylethylamine, pyridine, imidazole, N-methylmorpholine, sodium methoxide, diisopropylamine, and the like, inorganic bases, such as, for example, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; and any mixtures thereof.
• organic bases such as, for example, triethylamine, diisopropylethylamine, pyridine, imidazole, N-methylmorpholine, sodium methoxide, diisopropylamine, and the like
• inorganic bases such as, for example, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; and any mixtures thereof.
• Organic solvents that may be used in step (i) include, but are not limited to: nithles such as acetonitrile; alcohols, such as, for example, methanol, ethanol, isopropanol, n-butanol, and the like; halogenated hydrocarbons, such as, for example, dichloromethane, ethylene dichlohde, chloroform, and the like; esters, such as, for example, ethyl acetate, n-propyl acetate, isopropyl acetate, and the like; hydrocarbons, such as, for example, toluene, xylene, n-hexane, n-heptane, cyclohexane, and the like; ethers, such as, for example, 1 ,4-dioxane, tetrahydrofuran, and the like; aprotic polar solvents, such as, for example, N 1 N- dimethylformamide (
• Suitable temperatures for the reaction of step (i) may be less than about 120 0 C, less than about 100 0 C, less than about 60°C, or any other suitable temperatures.
• Suitable times for the reaction of step (i) may be from about 30 minutes to about 10 hours, or longer.
• Step (ii) involves preparation of the compound of Formula III by reacting the compound of Formula X with 3-thfluoromethyl-5,6,7,8-tetrahydro-1 ,2,4- triazole[4,3-a]pyrazine hydrochloride of Formula Xl, in the presence of
• the 3-trifluoromethyl-5,6,7,8-tetrahydro-1 ,2,4-thazole[4,3-a]pyrazine hydrochloride of Formula Xl may be prepared, e.g., using the process disclosed by J. Balsells et al., "Synthesis of [1 ,2,4]Thazolo[4,3- ⁇ ]piperazines via Highly Reactive Chloromethyloxadiazoles," Organic Letters, Vol. 7(6), pp. 1039-1042, 2005.
• the quantities of 3-trifluoromethyl-5,6,7,8-tetrahydro-1 ,2,4-triazole[4,3- a]pyrazine hydrochloride of Formula Xl may be less than about 3, or less than about 2, or less than about 1 molar equivalents, per mole of the compound of Formula X.
• the quantities of diisopropylethylamine may be less than about 3, or less than about 2, or less than about 1 , molar equivalents, per mole of the compound of Formula X.
• Solvents that may be used in step (ii) include, but are not limited to: nithles such as acetonitrile; halogenated hydrocarbons, such as dichloromethane, ethylene dichloride, and chloroform; hydrocarbons, such as toluene, xylene, n- hexane, n-heptane, and cyclohexane; ethers, such as 1 ,4-dioxane and
• Suitable temperatures for the reaction of step (ii) may be less than about 120 0 C, less than about 80 0 C, less than about 60°C, or any other suitable temperatures.
• Suitable times for the reaction of step (ii) may be from about 30 minutes to about 10 hours, or longer.
• Step (iii) involves reacting the compound of Formula III with a (R)-(+)-1- phenylalkylamine of Formula IV, to afford a compound of Formula V.
• the quantities of (R)-(+)-1-phenylalkylamine may range from about 1 to about 2 molar equivalents, per mole of the compound of Formula III.
• the reaction of step (iii) may be conducted in a solvent.
• Solvents that may be used include, but are not limited to: nitriles such as acetonitrile, alcohols such as methanol, ethanol, isopropyl alcohol, and n-butanol; ketones such as acetone, methyl isobutyl ketone, methyl ethyl ketone, and n-butanone; halogenated hydrocarbons such as dichloromethane, ethylene dichloride, and chloroform; esters such as ethyl acetate, n-propyl acetate, and isopropyl acetate;
• hydrocarbons such as toluene, xylene, n-hexane, n-heptane, and cyclohexane; ethers such as 1 ,4-dioxane and tetrahydrofuran; and any mixtures thereof.
• Suitable temperatures for the reaction of step (iii) may be less than about 150 0 C, less than about 120°C, less than about 80°C, less than about 60 0 C, or any other suitable temperatures.
• Suitable times for the reaction of step (iii) may be from about 30 minutes to about 10 hours, or longer.
• compositions comprising a therapeutically effective amount of sitagliptin or a pharmaceutically acceptable salt thereof that contains less than about 0.1 % of any individual impurity as determined using HPLC, together with one or more pharmaceutically acceptable excipients.
• compositions that include sitagliptin or a salt thereof may be formulated as: solid oral dosage forms such as, but not limited to, powders, granules, pellets, tablets, and capsules; liquid oral dosage forms such as, but not limited to, syrups, suspensions, dispersions, and emulsions; and injectable preparations such as but not limited to solutions, dispersions, and freeze dried compositions.
• Formulations may be in the form of immediate release, delayed release, or modified release.
• immediate release compositions may be conventional, dispersible, chewable, mouth dissolving, or flash melt preparations, and modified release compositions that may comprise hydrophilic or hydrophobic, or combinations of hydrophilic and hydrophobic, release rate controlling
• compositions may be prepared using any of techniques such as direct blending, dry granulation, wet granulation, and extrusion and spheronization.
• Compositions may be presented as uncoated, film coated, sugar coated, powder coated, enteric coated or modified release coated.
• Compositions of the present invention may further comprise one or more pharmaceutically acceptable excipients.
• compositions include, but are not limited to: diluents such as starches,
• pregelatinized starches lactose, powdered cellulose, microcrystalline cellulose, dicalcium phosphate, thcalcium phosphate, mannitol, sorbitol, sugar, and the like; binders such as acacia, guar gum, tragacanth, gelatin, polyvinylpyrrolidones, hydroxypropyl celluloses, hydroxypropyl methylcelluloses, pregelatinized starch, and the like; disintegrants such as starches, sodium starch glycolate,
• pregelatinized starches crospovidones, croscarmellose sodium, colloidal silicon dioxide, and the like
• lubricants such as stearic acid, magnesium stearate, zinc stearate, and the like
• glidants such as colloidal silicon dioxide and the like
• solubility or wetting enhancers such as anionic or cationic or neutral surfactants
• complex forming agents such as various grades of cyclodexthns and resins
• release rate controlling agents such as hydroxypropyl celluloses, hydroxymethyl celluloses, hydroxypropyl methylcelluloses, ethyl celluloses, methylcelluloses, various grades of methyl methacrylates, waxes, and the like.
• pharmaceutically acceptable excipients that are of use include, but are not limited to, film formers, plasticizers, colorants, flavoring agents, sweeteners, viscosity enhancers, preservatives, antioxidants, and the like.
• the processes of present invention are simple, cost-effective, ecologically friendly, reproducible, useful on a commercial scale, and robust, to produce salts of sitagliptin with high chemical and optical purity.
• Crystalline forms obtained by the present application can be characterized by their XRPD patterns, thermal analyses, and sprctroscopic methods such as infrared absorption spectrophotometry.
• PXRD data reported herein were obtained using copper Ka radiation, and were obtained using a Bruker AXS D8 Advance powder X-ray diffractometer.
• TGA analyses were carried out using a TGA Q500 instrument with a ramp of 10°C/minute, up to 250 0 C.
• the mixture is cooled to room temperature, followed by distillation to remove acetonitrile and afford a residue.
• Water (100 ml_) and ethyl acetate (500 ml_) are added to the residue, and the organic layer is separated.
• ketoamide i.e., 4- oxo-4-[3-(thfluoromethyl)-5,6-dihydro[1 ,2,4]thazolo[4,3a]pyrazin-7(8H)-yl]-1 -(2,4,5- trifluorophenyl)butan-2-one.
• lsopropyl alcohol (75 ml_) and (R)-(+)-1 - phenylethylamine (18.64 ml_) are added and the mixture is heated to 45-50°C for 4 hours.
• the isopropyl alcohol is distilled completely below 40°C to form a residue.
• Dichloromethane (200 ml_) and water (100 ml_) are mixed with the residue, followed by separation of the organic layer.
• the aqueous layer is extracted with dichloromethane (200 ml_).
• the organic layers are combined, washed with brine, dried over sodium sulphate, and distilled to afford a residue, which, on purification results in the title compound (28.7g, 42.8% yield).
• EXAMPLE 4 Preparation of 7-[1 -oxo-(3R)-(R-1-phenylethylamino)-4(2,4,5- trifluorophenyl)-butyl)-3-trifluoromethyl-5,6,7,8-tetrahydro-1 ,2,4-triazolo[4,3-a] pyrazine (Formula Vl).
• Dimethoxyethane 35 mL is charged into a round bottom flask and is cooled to -40 0 C, followed by addition of sodium borohydride (1.12 g) in one portion. Methanesulfonic acid (4.7 mL) is slowly added, with continuous stirring at -40°C.
• dimethoxyethane (50 ml_) and (Z)-7-(1 -oxo-3(R)-1 - phenylethylamino)-4-(2,4,5-trifluorophenyl)-but-2-enyl)-3-tnfluoronnethyl-5,6,7,8- tetrahydro-1 ,2,4-triazolo[4,3a]pyrazine (5 g) are combined and stirred for 30 minutes at -40 0 C.
• This solution is added to the solution of sodium borohydhde and methanesulfonic acid over 30 minutes, while maintaining a temperature of -40 0 C.
• EXAMPLE 5 Preparation of 7-[1 -oxo-(3R)-(R-1-phenylethylamino)-4(2,4,5- trifluorophenyl)-butyl)-3-trifluoromethyl-5,6,7,8-tetrahydro-1 ,2,4-triazole[4,3-a] pyrazine hydrochloride.
• Dimethoxyethane (171 ml_) is charged into a flask and cooled to -40 0 C, followed by addition of sodium borohydride (7.3 g) in one lot. To this mixture, methanesulfonic acid (31.02 ml_) is slowly added, with constant stirring at -40°C, over 45-60 minutes.
• the mixture is stirred at this temperature for 16 hours.
• the mixture is brought to 0°C, followed by addition of ethyl acetate (600 ml_).
• Water (330 ml_) is added, the mixture is stirred for 15 minutes, and the organic layer is separated.
• the aqueous layer is extracted with ethyl acetate (720 ml_).
• the two organic layers are combined and washed with brine solution (250 ml_).
• the organic layer is separated, dried over sodium sulphate and then distilled under reduced pressure at 40 0 C until 10-15% of the solvent volume remains in the flask, at which point solid begins to precipitate.
• Dimethoxyethane (300 ml_) and sodium borohydhde (7.4 g) are charged into a flask and cooled to -40 0 C.
• methanesulfonic acid (31.02 ml_) is slowly added with constant stirring at -40 0 C, over 40 minutes.
• the formed solid is filtered, washed with chilled ethyl acetate (60 ml_) and dried under reduced pressure at 45°C for 6 hours, to afford the title compound (19.0 g; chiral purity by HPLC: 99.09%).
• EXAMPLE 7 Preparation of 7-[1 -oxo-(3R)-(R-1-phenylethylamino)-4(2,4,5- trifluorophenyl)-butyl)-3-trifluoromethyl-5,6,7,8-tetrahydro-1 ,2,4-triazolo[4,3-a] pyrazine hydrochloride.
• Dimethoxyethane (240 mL) and sodium borohydhde (5.6 g) are charged into a flask and cooled to -40 ⁇ 5°C.
• methanesulfonic acid (31.02 mL) is slowly added with constant stirring at -40 0 C, over 30 minutes, and further maintained for 30 minutes.
• a mixture of above obtained residue, dimethoxyethane (60 mL), and isopropyl alcohol (40.5 mL) is slowly added at -40 0 C, over 30 minutes, and the mass is maintained for 1 hour.
• Ethyl acetate (300 mL) is added over 15 minutes, followed by addition of water (300 ml_) at 12°C.

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