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') or (4R,5S)-cis-1,3-dibenzyl-5-methoxy- or ethoxycarbonyl-2-oxoimidazolidine-4-carboxylic acid (Ib'), comprising preferentially crystallizing (la') or (Ib') from a supersaturated solution where (Ia') and Ib') are copresent in the presence of crystals of the same type of optically active half ester as that to be crystallized is disclosed.
一种制备光学活性(4S,5R)-顺式-1,3-二苄基-5-甲氧基-或乙氧基羰基-2-氧代
咪唑烷-4-
羧酸(Ia')或(4R,5S)-顺式-1,3-二苄基-5-甲氧基-或乙氧基羰基-2-氧代
咪唑烷-4-
羧酸(Ib')的方法、本发明公开了(Ia')和(Ib')共存的过饱和溶液中(la')或(Ib')的结晶方法,该方法包括在与待结晶的光学活性半
酯类型相同的晶体存在下,优先从该溶液中结晶出(la')或(Ib')。