Design and synthesis of conformationally constrained arginal thrombin inhibitors

A series of conformationally constrained arginal thrombin inhibitors was prepared starting from 5,6 or 5,7 bicyclic lactamic structures, that an indirect approach of X-ray structure-based drug design indicated as D-Phe-Pro dipeptide mimetics. The tetrahydroquinolyl sulfonamido derivative Ig (LR-D/009) displayed the best inhibitory potency (IC50 = 0.018 μm), with good selectivity over plasmin and trypsin.