A series of substituted aryl malonamates have been prepared. These compounds are analogues of aryl phenaceturates where the amido side chain has been replaced by a retro- amide. Like the phenaceturates, these compounds are substrates of typical class A and class C β-lactamases, particularly of the latter, and of soluble DD-peptidases. The effect of substituents α to the ester carbonyl group on turnover by these enzymes is similar to that ...