Disclosed are methods of synthesizing enantioenriched difluoroalkylcyclopropyl amino esters and their salts, such as the dicyclohexylamine salt of (1S,2R)-2-(difluoromethyl)-1-(propoxycarbonyl)cyclopropane carboxylic acid. These compounds are useful intermediates in the synthesis of viral protease inhibitors.

The present invention provides a method for producing an atropisomer of a pyrrole derivative having excellent mineralocorticoid receptor antagonistic activity, and an intermediate thereof. A method for producing an atropisomer of a pyrrole derivative using a compound represented by (B) [wherein R.sup.1 represents a C1-C4 alkyl group, and R.sup.2 represents a 2-hydroxyethyl group or a carboxymethyl group] as a production intermediate. ##STR00001##

The invention provides methods of synthesizing a viral protease inhibitor in high yield, without using expensive catalysts or challenging reaction conditions.

The invention provides methods of synthesizing a viral protease inhibitor in high yield, without using expensive catalysts or challenging reaction conditions.

Disclosed are methods of synthesizing racemic 2-(difluoromethyl)-1-(alkoxycarbonyl)-cyclopropanecarboxylic acids and 2-(vinyl)-1-(alkoxycarbonyl)-cyclopropanecarboxylic acids and their salts, such as the dicyclohexylamine salt. Also disclosed are methods for preparing enantioenriched (1R,2R)-1-((tert-butoxycarbonyl)amino)-2-(difluoromethyl)cyclopropane-1-carboxylic acid and esters of the same. These compounds are useful intermediates in the synthesis of viral protease inhibitors.

The present invention provides a method for producing an atropisomer of a pyrrole derivative having excellent mineralocorticoid receptor antagonistic activity, and an intermediate thereof. A method for producing an atropisomer of a pyrrole derivative using a compound represented by (B) [wherein R.sup.1 represents a C1-C4 alkyl group, and R.sup.2 represents a 2-hydroxyethyl group or a carboxymethyl group] as a production intermediate.

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The present invention provides an improved process for the preparation of a compound of formula (I), which comprises the steps of: formula (I), (a) reacting isovaleraldehyde of formula (II) and alkyl cyanoacetate of formula (III) optionally in presence of salts of weak acid and weak base or weak base in a suitable solvent to get 2-cyano-5-methyl-hex-2-enoic acid alkyl ester of formula (IV); (b) reacting 2-cyano-5-methyl-hex-2-enoic acid alkyl ester of formula (IV) with a suitable cyanide source in water or in an organic solvent or mixture thereof to get 2-isobutylsuccinonitrile of formula (V); (c) obtaining optionally 2-isobutylsuccinonitrile of formula (V) by reacting isovaleraldehyde of formula (II) and alkyl cyanoacetate of formula (III) in presence of suitable cyanide source in water or in an organic solvent or mixture thereof in single step; (d) converting 2-isobutylsuccinonitrile of formula (V) to racemic 3-cyano-5-methyl-hexanoic acid or salt thereof of formula (VI) with a genetically modified nitrilase enzyme (Nit 9N_56_2) in water or optionally with an organic co-solvent at appropriate pH and temperature; (e) converting racemic 3-cyano-5-methyl-hexanoic acid or salt thereof of formula (VI) to racemic alkyl 3-cyano-5-methyl-hexanoate of formula (VII) by treatment with alcohol (R3OH) and acidic catalyst or alkyl halide (R3X) in presence of a base in a suitable solvent or a mixture of solvents thereof; (f) obtaining (S)-alkyl 3-cyano-5-methyl-hexanoate of formula (VIII) and (R)-3-cyano-5-methyl-hexanoic acid or salt thereof of formula (X) by enzymatic enantioselective hydrolysis in water or organic solvent or a mixture thereof from racemic alkyl 3-cyano-5-methyl-hexanoate of formula (VII); (g) obtaining optionally the compound of formula (VII) by racemizing unwanted (R)-3-cyano-5-methyl-hexanoic acid or salt thereof of formula (X) or substantially enriched (R)-3-cyano-5-methyl-hexanoic acid salt thereof of formula (X) in presence of a base in organic solvent or a mixture thereof; (h) converting (S)-alkyl 3-cyano-5-methyl-hexanoate of formula (VIII) to pregabalin of formula (I) by hydrolyzing ester group with suitable alkali or alkaline earth metal base followed by hydrogenation optionally in one pot in a solvent selected from water or other organic solvents or a mixture thereof in presence of a suitable hydrogenation catalyst. ##STR00001##

The invention provides methods of synthesizing compounds in an asymmetric or enantioenriched fashion, wherein the compounds are useful intermediates in the synthesis of viral protease inhibitors.

The present invention provides a method for producing an atropisomer of a pyrrole derivative having excellent mineralocorticoid receptor antagonistic activity, and an intermediate thereof. A method for producing an atropisomer of a pyrrole derivative using a compound represented by (B) [wherein R.sup.1 represents a C1-C4 alkyl group, and R.sup.2 represents a 2-hydroxyethyl group or a carboxymethyl group] as a production intermediate. ##STR00001##

A process for producing alkyl R-lactate from an initial compound comprising substructure (I)

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is provided. The process involves producing an intermediate comprising R,R- and S,S-lactide from the initial compound, wherein the initial compound is subjected to stereoisomerisation conditions; and reacting at least a portion of the intermediate with an alkyl alcohol to produce a product comprising alkyl R-lactate, wherein alkyl R-lactate is produced in the presence of an enzyme. Also provided are processes for the production of R-lactic acid, oligomeric R-lactic acid, R,R-lactide, poly-R-lactic acid and stereocomplex lactic acid.