Asymmetric reduction of ethyl α-chloroacetoacetate (3) with Baker's  yeast followed by treatment with sodium ethoxide afforded a mixture of ethyl  (2R,3S)-( 8) and (2S,3S)-2,3-epoxybutanoate (9)  (8/9, 85:15), which could be converted into the optically pure methyl  (2R,3S)-2,3-epoxybutanoate (25) via one recrystallization of the  brucine salt of the diastereomeric mixture of the corresponding epoxy acid.
                                    用贝克酵母不对称还原δ-
氯乙酰乙酸乙酯(3),然后用
乙醇钠处理,得到(2R,3S)-( 8)和(2S,3S)-2,3-环氧
丁酸乙酯(9)的混合物(8/9,85:通过对相应环氧酸非对映异构体混合物的布鲁
氨酸盐进行一次重结晶,可将其转化为光学纯度较高的 (2R,3S)-2,3-环氧
丁酸甲酯 (25)。