Patent ID: 7060471

Claim:
A stereoselective chemoenzymatic process for the synthesis of optically enriched trans alkyl phenylglycidate in its enantiomeric forms alkyl(2S,3R)-phenylglycidate and alkyl(2R,3S)-phenylglycidate of formulae 7 and 8 respectively, wherein said process comprises steps of, a. halogenating alkyl cinnamate of formula 1 by action of a halogenating agent to obtain halohydrins of formula 2, where X represents bromine or iodine, and R′ represents C-1 to C-5 alkyl group; b. acylating the halohydrins of formula 2 using an acyl anhydride in presence of a base to trans alkyl 3-acyloxy-2-halo-3-phenylpropanoates of formula 3-; c. incubating the trans alkyl 3-acyloxy-2-halo-3-phenylpropanoates of formula 3 with dry powder of the lipase in an aqueous buffer phase optionally in presence of an organic medium at a temperature range of 10–40° C. for the time duration in the range of 30–55 hr. to facilitate the reaction to get hydrolysed alkyl(2R,3R)-2-halo-3-hydroxy-3-phenylpropanoates of formula 4 and unhydrolysed alkyl(2S,3S)-3-acyloxy-2-halo-3-phenylpropanoates of formula 5; d. separating the hydrolysed alkyl(2R,3R)-2-halo-3-hydroxy-3-phenylpropanoates of formula 4 and unhydrolysed alkyl(2S,3S)-3-acyloxy-2-halo-3-phenylpropanoates of formula 5 by conventional method of chromatography; e. incubating the optically enriched unhydrolised phenyl proponoates of formula 5 with crude dry powder of lipase from Aspergillus niger in an aqueous buffer phase in presence of an organic solvent to further improve the enantiopurity; f. reacting the optically enriched products of formula 5 with an acid to furnish optically enriched alkyl(2S,3S) 2-halo-3-hydroxy-3-phenylpropanoate of formula 6, and g. treating the compounds of formulae 4 and 6 with an alkali or an acid in an organic or aqueous phase which leads the formation of epoxide ring by cyclisation to furnish optically enriched alkyl(2S,3R)-phenylglycidate and alkyl(2R,3S)-phenylglycidate of formulae 7 and 8 respectively.