The coronavirus main protease, M-pro, is considered a major target for drugs suitable to combat coronavirus infections including the severe acute respiratory syndrome (SARS). In this study, comprehensive HPLC- and FRET-substrate-based screenings of various electrophilic compounds were performed to identify potential M-pro inhibitors. The data revealec that the coronaviral main protease is inhibited by aziridine- and oxirane-2-carboxylates. Among the trans-configured aziridine-2.3-dicarboxylates the Gly-Gly-containing peptide 2c was found to be the most potent inhibitor. (c) 2005 Elsevier Ltd. All rights reserved.