Design, Synthesis, and Activity of 2,6-Diphenoxypyridine-Derived Factor Xa Inhibitors^1,2

A novel series of 2,6-diphenoxypyridines has been designed to inhibit factor Xa, a serine protease strategically located in the coagulation cascade. The evolution from the photochemically unstable bisamidine (Z,Z)-BABCH to potent bisamidine compounds with a pyridine heterocycle as the core scaffold has been achieved. The most potent compound in the series, 6h, has a K-i for human factor Xa of 12 nM. The selectivity of 6h against bovine trypsin and human thrombin was greater than 90- and 1000-fold, respectively. Two proposed modes of binding of 6h Do factor Xa are made based on the crystal structures of 6h by itself and of 6h bound to bovine trypsin.