Chiral resolution of an intermediate in diltiazem synthesis using lipase PS immobilized with sucrose

A method for the preparation of (2S,3S)-threo-alkyl-2-hydroxy-3-(4-methoxyphenyl)-3-(2-X-phenylthio)propio nates and (2R,3R)-threo-alkyl-2-acyloxy-3-(4-methoxypheny-1)-3-(2-X-phenyl-thio)prop ionates according to formulae 1 and 2, below:

• ##STR6## comprising reacting in anhydrous solvent or anhydrous solvents a racemic compound of formula 1, wherein X is selected from the group consisting of NO.sub.2, NH.sub.2, NHCOCH.sub.3, NHCOCF.sub.3, NHCO.sub.2 CH.sub.3, and NHCHO and R.sub.1 is a methyl or ethyl group with an acylating reagent selected from the group consisting of acid anhydrides vinyl, esters and acetoneoxime acetate and a catalytically effective amount of Amano PS lipase which is immobilized in the presence of saccharose under conditions which provide for the acylation of the racemic compound of formula 1, and separating and recovering the resultant (2R,3R)-threo-alkyl-2-acyloxy-3-(4-methoxyphenyl)-3-(2-X-phenylthio)propio nate of formula 2 from the (2S,3S)-threo-alkyl-2-hydroxy-3-(4-methoxyphenyl)-3-(2-X-phenylthio)propio nate compound according to formula 1.