Novel epoxysuccinyl peptides Selective inhibitors of cathepsin B, in vitro

A series of new epoxysuccinyl peptides were designed and synthesized to develop a specific inhibitor of cathepsin B. Of these compounds, N ‐(L‐3‐ trans ‐ethoxycarbonyloxirane‐2‐carbonyl)‐L‐isoleucyl‐L‐proline (compound CA‐030) and N ‐(L‐3‐ trans ‐propylcarbamoyloxirane‐2‐carbonyl)‐L‐isoleucyl‐L‐proline (compound CA‐074) were the most potent and specific inhibitors of cathepsin B in vitro. The carboxyl group of proline and the ethyl ester group or n ‐propylamide group in the oxirane ring were necessary, the ethyl ester group or the n ‐propylamide group being particularly effective for distinguishing cathepsin B from other cysteine proteinases such as cathepsins L and H, and calpains.