Cysteine protease inhibitors containing small rings.

Since the discovery of E-64 in 1978 as potent cysteine protease inhibitor a variety of inhibitors containing small rings as electrophilic building blocks responsible for enzyme inhibition have been developed. In this review we summarize new aspects concerning epoxysuccinyl peptides derived from E-64 and discuss inhibition potency, selectivity and mechanisms of peptidic and peptidomimetic inhibitors containing epoxide, aziridine, thiirane, cyclopropane, beta-lactam and beta-lactone rings as electrophilic fragments.