Specificity of extended O-aryloxycarbonyl hydroxamates as inhibitors of a class C β-lactamase.

Class C β-lactamases have previously been shown to be efficiently inactivated by O-aryloxycarbonyl hydroxamates. O-Phenoxycarbonyl-N-benzyloxycarbonylhydroxylamine (1) and O-phenoxycarbonyl-N-(R)-[(4-amino-4-carboxy-1-butyl)oxycarbonyl]hydroxylamine (2), for example, were found to be effective inactivators. The present paper describes a structure-activity study of these molecules to better define the important structural elements for high inhibitory activity. The results show that a well-positioned hydrophobic element (which may interact with the Tyr221 residue of the enzyme) and a negatively charged element, e.g. a carboxylate group (which may interact with Arg204), are required for high reactivity with the enzyme. The new compounds were found to inactivate by forming a carbonyl cross-linked enzyme (probably Ser64OCONHLys 315) as for 1 rather than the inert hydroxamoyl derivative observed with 2.