The chemistry of penicillanic acids. Part III. A route to 1,2-secopenicillins

Treatment of 6β-(triphenylmethylamino)penicillanates with certain alkylating agents in the presence of strong anhydrous bases causes S-alkylation and cleavage of the thiazolidine ring between the sulphur atom and C-2. The scope and possible mechanism of the reaction are discussed. A typical product, (3R,4R)-1-(1-p-methoxybenzyloxycarbonyl-2-methylprop-1-enyl)-4-methylthio-3-(triphenylmethylamino)azetidin-2-one, has been converted into analogues of penicillins and cephalosporins containing a non-fused β-lactam ring.