Abstract: The present invention provides an enzymatic process for the preparation of (S)-5-(4-Fluoro-phenyl)-5-hydroxy-1morpholin-4-yl-pentan-1-one by the reduction of 1-(4-Fluoro-phenyl)-5-morpholin-4-yl-pentane-1,5-dione by using a suitable enzyme or by the resolution of (R,S)-5-(4-Fluoro-phenyl)-5-hydroxy-1morpholin-4-yl-pentan-1-one by using an enzyme. The present invention also provides process for the preparation of Ezetimibe comprising the steps of a) protecting the compound (S)-5-(4-Fluoro-phenyl)-5-hydroxy-1morpholin-4-yl-pentan-1-one with hydroxy protecting group b) hydrolyzing the obtained compound c) condensing with a chiral auxiliary d) reacting with an protected imine compound e) converting to alkyl ester f) cyclizing and g) deprotecting to obtain Ezetimibe.

Abstract: The present invention relates to an improved process for the preparation of cis-nucleoside derivative of formula-1 involving chlorination of the compound of formula-2 followed by reaction with compound of formula-3 in presence of a base to get compound of formula-4, reacting the compound of formula-4 with an alkyl halide (RiX) to get a quaternary ammonium salt then with cytosine derivative of formula-5 to provide the compound of formula-6, optionally de-protecting the compound of formula-6 to the compound of formula-7, reducing compound of formula-7 with metal catalyst in presence of a buffer solution, then adding an organic acid to get the compound of formula-8, and converting the compound of formula-8 to cis-nucleoside derivative of formula-1. The present invention further relates to novel cis-nucleoside derivative of formula-8. The present invention also relates to a pharmaceutical composition comprising cis-nucleoside derivative of formula-1 with excipients.