Their inhibition has been studied by Testero and co-workers, who tested an extensive series of thiirane and epoxide analogs of (2S, 3R)-2-benzyl-3,4-epoxybutanoic acid (BEBA), in which they modified the original BEBA phenyl ring to alkyl side chains or rings. Mobashery and co-workers have developed thiirane-and epoxide-containing molecules such as (R)-ND-336 which have been shown to inhibit matrix metalloproteinase (MMP) through covalent interaction with nucleophilic residues in the active site. Some recent studies have reported the application of epoxides to the inhibition of bacterial enzymes. Epoxycephalosporins reported by Lebedev inhibited class A β-lactamases; however, their study was inconclusive on the exact mechanism by which the inhibition took place. Fosfomycin, which is the only phosphonate in the clinic, inhibits uridine diphosphate-N-acetylglucosamine enolpyruvyl transferase (MurA), an enzyme involved in peptidoglycan synthesis. Nucleophilic attack of the active site cysteine residue of MurA, Cys115, on the fosfomycin epoxide ring inactivates MurA, disrupting cell wall synthesis and thus killing the bacterium. 281