Transacylation of cephalosporin; isolation and reactions of the imidate esters

Abstract

The reaction of the imidate ester of methyl 7-acetamidoceph-3-em-4-carboxylate (2) and phenylacetyl chloride was followed by ¹³C n.m.r. spectroscopy, which disclosed the intermediacy of the adduct of (2) with the acyl chloride. Transacylations of methyl 7-([1-¹³C]acetamido)ceph-3-em-4-carboxylate (8) and methyl 7-{±)-5-benzamido-5-methoxycarbonyl[1-¹³C]valeramido}ceph-3-em-4-carboxylate (9) were also found to proceed through direct atack of the acyl chloride on the respective imidate ester.