Patent ID: 7560585

Claim:
A process for preparation of (S)-α-cyano-3 -phenoxybenzyl-(S)-2-(4-chlorophenyl) isovalerate (S,S isomer), said process comprising the steps of: a) crystallizing (RS)-α-cyano-3 -phenoxybenzyl-(S)-2-(4-chlorophenyl) isovalerate (diastereomer-A), in the presence of crystals or a slurry of S,S isomer of a purity of 99% or greater in a solvent that is a saturated solution of 1, 2-dichloroethane to obtain crystals of S,S isomer from mother liquor; b) epimerizing the mother liquor enriched with R,S isomers, and c) recycling the mother liquor for further crystallization.