Guanidinophenyl-Substituted Enol Lactones as Selective, Mechanism-Based Inhibitors of Trypsin-Like Serine Proteases

We have synthesized four guanidinophenyl-substituted protio enol and iodo enol lactones (3-(4- guanidinophenyl)-6-methylidenetetrahydro-2-pyranone (1), 3-(4-guanidinophenyl)-6-(E)-(iodomethylidene) tetrahydro-2-pyranone (2), 4-(4-guanidinophenyl)-6-methylidenetetrahydro-2-pyranone (3), and 4-(4-guanidinophenyl)-6-(E)-(iodomethylidene)tetrahydro-2-pyranone (4)) and tested them for inhibitory activity against some trypsin-like enzymes, namely trypsin, urokinase, tissue plasminogen activator (t-PA), plasmin, and thrombin, as well as α-chymotrypsin and human neutrophil elastase (HNE). The β-aryl-substituted protio lactone 3 was a potent alternate substrate inhibitor of trypsin and urokinase. The α-aryl-substituted iodo lactone 2 was a permanent inactivator of urokinase, plasmin, t-PA, thrombin, and α-chymotrypsin, exhibiting a relatively high specificity for the former two enzymes. In general, these compounds showed a preference for inactivating trypsin-like enzymes over α-chymotrypsin and HNE. Also, within the class of trypsin-like enzymes, there was generally good selectivity of inhibition.