Synthesis and reactivity with β-lactamases of a monobactam bearing a retro-amide side chain

The monobactam sodium 3-benzylcarbamoyl-2-oxo-1-azetidinesulfonate, bearing a retro (vs classical β-lactam)-amide side chain, has been synthesized and the kinetics of its reaction with typical β-lactamases studied. The new compound is generally a poorer substrate than the analogous compound with a normal side chain but its formation of a transiently stable complex with a class C β-lactamase sustains the retro-amide side-chain concept.