A simple and efficient synthesis of the γ-lactam analogue of β-lactam antibiotics. Ring-expansion of penicillins to homopenicillins

Abstract

Irradiation of the β-ketosulphoxonium ylide (2), prepared easily from the benzylpenicillin methyl ester (1), with u.v. light results in the smooth formation of the corresponding homopenicillin methyl ester (3) which is hydrolysed to give benzylhomopenicillin (4) quantitatively.