Chemistry of cephems: C-4 substitution and sulphoxide de-oxygenation reactions

Abstract

The anion derived from ceph-3-em esters adds readily to Michael acceptors to give C-4 disubstituted ceph-2-ems. Oxidation of a typical adduct, such as the 4-cyanoethyl-4-diphenylmethyl ester, followed by ester hydrolysis and decarboxylation, gives the 4-cyanoethylceph-3-em sulphoxide which is easily reduced to the sulphide. Furthermore, zinc-acetic acid in DMF (dimethylformamide) is found to be an effective, mild reagent for the de-oxygenation of ceph-2-em sulphoxides.