Patent ID: 9518028
Filing Date: 2016-12-13
CPC Classification: A61P,C07D,C07F

Claim Text:
1. A process for preparation of the compound of formula (4), which comprises the steps of: Step 1) reacting (R)-(−)-Ethyl 4-cyano-3-hydroxy butyrate of formula (1) with tertiarybutyldimethylsilyl chloride in presence of solvent, selected from the group consisting of dichloromethane, dichloroethane and chloroform, and imidazole at a temperature in the range of 20° C. to 35° C. for the period of 18 hours to 22 hours to obtain (R)-(−)-Ethyl 4-cyano-3-(tertiarybutyldimethylsilyloxy) butyrate of formula (2); Step 2) hydrolysing the (R)-(−)-Ethyl 4-cyano-3-(tert-butyldimethylsilyloxy) butyrate of formula (2) in presence of solvent, selected from the group consisting of methanol, dichloromethane, dichloroethane and chloroform, and a base, selected from the group consisting of potassium carbonate, sodium bicarbonate, sodium hydride and sodium hydroxide, at a temperature in the range of 8° C. to 18° C. for the period of 2 hours to 4 hours to obtain (R)-4-cyano-3-(tert-butyldimethylsilyloxy) butyric acid of formula (3); Step 3) esterifying (R)-4-cyano-3-(tert-butyldimethylsilyloxy) butyric acid of formula (3) by using catalyst, selected from the group consisting of 4-dimethylaminopyridine, tert-butyl ethyl fumarate and dicyclohexylcarbodiimide, and di-tert-butyl dicarbonate in presence of solvent, selected from the group consisting of t-butanol, dichloromethane, dichloroethane and chloroform, and a base, selected from the group consisting of potassium carbonate, sodium bicarbonate, sodium hydride and sodium hydroxide, at a temperature in the range of 20° C. to 35° C. for the period of 2 hours to 5 hours to obtain (R)-tertiary butyl 4-cyano-3-(tert-butyldimethylsilyloxy) butyrate of formula (4).