New polycyclic β-lactams. Synthesis of 2a,3-dihydroazeto[1,2-a]quinoline-1,4(2H)-diones, structural analogues of the carbacephalosporin antibiotics

A method has been developed for the preparation of dihydroxydihydroazeto[1,2-a]quinoline-1,4(2H)-diones (1). The synthesis involved, as a key step, the completion of the polycyclic β-lactam system by a modified Bischler–Napieralski reaction. It was illustrated by the synthesis of (±)-7,8-dihydroxy-3,3-dimethyl-2-phenoxyacetamido-2a,3-dihydroazeto[1,2-a]quinoline-1,4(2H)-dione (20), which is structurally related to the carbacephalosporin antibiotics.