Synthesis of new N-sulfonyl monocyclic β-lactams and the investigation of their antibacterial activities

New monocyclic β-lactams 4-6 were synthesized by a ketene-imine [2+2] cycloaddition reaction. The prepared monocyclic -lactams 4-6 were cleaved by ceric ammonium nitrate (CAN) to give NH β- lactams 7-9. The NH -β- lactams were converted to N-sulfonyl -lactams 10-21 by treatment with four different sulfonyl chlorides in the presence of Et3N and 4-N,N-dimethylaminopyridine (DMAP). Some of these monocyclic β-lactams were active against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa.