A New Short Cut Route to 3-Norcephalospolins

Tanaka, H.; Kameyama, Y.; Sumida, S.-i.; Yamada, Y.; Tokumaru, Y.; Shiroi, T.; Sasaoka, M.; Taniguchi, M.; Torii, S. Synlett 1991, 888.

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.