Functional Derivatives of a New Ring System, 1H,4H-Azeto[2,1-b]thiazolo[3′,2′:1,5]pyrrolo[3,4-d][1,3]thiazine

The reaction of 7-β-phenylacetamido-3-formylceph-3-em-4-carboxylic acid benzhydryl ester with D-penicillamine gives rise to a new fused tetracyclic system.