Process for producing optically active alpha-isopropyl-p-chlorophenylacetic acid.

摘要

A process for producing optically active alpha -isopropyl-p-chlorophenylacetic acid (ICPA) of the formula: <CHEM> wherein the symbol * stands for an asymmetric carbon atom, which comprises subjecting an ICPA ester in the form of a racemic mixture corresponding to the formula (II) <CHEM> wherein X1, X2 and X3 are independently halogen atoms, or two of them are independently halogen atoms and the third is hydrogen atom or a lower alkyl group, and the meaning of the symbol * are the same as defined above, to optical resolution by preferential crystallization from an organic solvent at a degree of supersaturation of not more than 150 % at the intended crystallization temperature to separate an optically active ICPA ester of the formula (II); subjecting the optically active ICPA ester obtained to hydrolysis with retaining its configuration to give the corresponding optically active ICPA of the formula (I) ; and subjecting the undesired optically active ICPA ester remaining in the mother liquor after the optical resolution to racemization by a strong organic base to form the racemic mixture of the ICPA ester, which can be subjected to another optical resolution.