Synthesis of Novel 3-spirocephalosporins and Evaluation of their Antibacterial Activity.

Abstract

Background and objectives: Despite the well-known antibacterial activity of cephalosporins, their analogous spirocyclic derivatives have not been adequately evaluated. Thus, this work aimed to prepare a series of novel 3-spirocephalosporins and evaluate their antibacterial activity.

Materials and methods: Novel 3-spirocephalosporins were prepared through a one-pot thioalkylation of chloromethyl cephalosporin GCLE with a range of 1,2,4-triazolidine-3- thiones, followed by intramolecular Michael addition to the generated dihydrothiazine ring. The reaction was performed at room temperature under basic conditions (K2CO3, acetone, H2O). The antibacterial activities of the synthesized compounds were evaluated against a panel of Gram-positive and Gram-negative bacteria.

Results: Most targets were obtained in moderate yield, and their structures were confirmed by ¹H and ¹³C NMR spectral techniques. All the tested compounds exhibited antibacterial activity against methicillin-resistant S. aureus.

Conclusion: Seven novel thiazolidine-bearing 3-spirocephalosporins were prepared, and most of them were potent against Gram-positive bacteria. Likely, the replacement of 1,2,4- triazolidine-3-thiones with other heterocycles containing bidentate nucleophiles in advantageous positions could lead to different biologically active spirocephalosporins.