To a cooled (5° C.), stirred solution of 0.897 g. of benzhydryl 7-(2-thienylacetamido)-3-(1-acetoxyethyl)-2-cephem-4-carboxylate in 80 ml. of chloroform was added a solution of 0.348 g. of 85 percent m-chloroperbenzoic acid in 3 ml. of chloroform. The reaction mixture was allowed to stir with cooling for 30 minutes after which time it was transferred to a separatory funnel with the aid of additional chloroform and washed successively with sodium bicarbonate solution (2X), and brine (2X) and dried over anhydrous sodium sulfate. The residue obtained by evaporation in vacuo to a froth which was chromatographed on a silica gel column using a toluene-ethyl acetate gradient to give 0.243 g. (26 percent) of what was labeled diastereoisomer I and 0.514 g. (55 percent) of what was labeled diastereoisomer II of the title product; isomer I coming off the column first.
