The stability of the 1-carba-1-dethiacephalosporin framework has allowed the synthesis of a range of 3-sulfonyl-1-carba-1-dethiacephems unavailable for a variety of reasons in the cephem arena. The known p-nitrobenzyl 7 beta-(phenoxyacetamido)-3-[[(trifluoromethyl)sulfonyl]oxy]-1-carba -1- dethia-3-cephem-4-carboxylate served as a precursor to this series of compounds. Displacement of the enol triflate with various sulfinates in acetonitrile or DMF and deprotection of the intermediates led to 7 beta-[(2-amino-4-thiazolyl)(methoxyimino)acetyl]amino]- 3-[alkyl(aryl)sulfonyl]-1-carba-1-dethia-3-cephem-4-carboxyl ic acids. The 3-sulfonyl-1-carba-1-dethiacephems display potent activity against both Gram-positive and Gram-negative bacteria. The following MIC's (microgram/mL) for the 3-cyclopropyl sulfone are representative: Staphylococcus aureus = 4, Streptococcus pyogenes = 1, Haemophilus influenzae = 0.25, Escherichia coli = 0.03, Enterobacter cloacae = 0.25, Proteus rettgeri = 0.25. The excellent in vitro antibacterial activity of this series indicates the potential of the carbacephalosporin framework for exploring substituents which are unknown or which produce unstable cephems.

The 1‐carba‐1‐dethiacephalosporin p‐nitrobenzyl ester (I) is transesterified via the acid (II) to form the allyl (IVa) and the diphenylmethyl ester (IVb).