As determined by HPLC analysis of the diastereomeric mixture 2b, according to ref 8. bHydrolyses were stopped at a 50% consumption of theoretical amount of 1 N NaOH.'Determined by 200-MHz'H NMR analysis of derivatives 2e and 2f the COCHB resonances were at 1.96 ppm for R isomer and 1.94 ppm for the S isomer. dAt 50% consumption of 1 equiv of base, ee for this compound was 98%.
