Method of obtaining optically active half esters.

摘要

A method of separating optically active half esters comprising optically resolving a mixture of a (4S,5R)-1,3-dibenzyl-5-alkoxy or alkenyloxycarbonyl-2-oxoimidazolidine-4-carboxylic acid and a (4R,5S)-1,3-dibenzyl-5-alkoxy or alkenyloxycarbonyl-2-oxoimidazolidine-4-carboxylic acid, each being represented by the formula (I): <CHEM> wherein R1 is an alkyl group or an alkenyl group, each having 1 to 5 carbon atoms; Bzl is a nenzyl group: * indicates an asymmetric carbon atom; and the 4- and 5-positions are a cis-configuration, using an optically active d- or 1-amine represented by the formula (II): <CHEM> wherein R2 and R3 are each a hydrogen atom, a halogen atom or methyl group; and indicates an asymmetric carbon atom; and the eforementioned half esters are disclosed. A method for the preparation of an optically active (4S,5R)-cis-1,3-dibenzyl-5-methoxy- or ethoxycarbonyl-2-oxoimidazolidine-4-carboxylic acid (Ia min ) or (4R,5S)-cis-1,3-dibenzyl-5-methoxy- or ethoxycarbonyl-2-oxoimidazolidine-4-carboxylic acid (Ib min ), comprising preferentially crystallizing (Ia min ) or (Ib min ) from a supersaturated solution where (Ia min ) and (Ib min ) are copresent in the presence of crystals of the same type of optically active half ester as that to be crystallized, is also disclosed.