A New Short Cut Route to 3-Norcephalosporins¹

Abstract

3-Norcephems 1 bearing heteroatom substituents directly attached to C(3)-position were prepared starting from penicillin G through a new short cut route involving Michael addition of amines, azide or thiols to allenic esters 6, 2-[2-oxo-3-phenylacetylamino-4-(phenylsulfonylthio)azetidin-1-yl]-2,3-butadienoic acid esters, and sequential ring closure to the six-membered ring.