Organic phosphorus compounds. 5. (4-Benzothiazol-2-ylbenzyl)amidophosphonate as potent calcium antagonistic vasodilators.

Structural modifications of the calcium antagonist fostedil (KB-944) and their coronary vasodilator activity are described. Amidophosphonates 4a-m, lactam amidophosphonates 7a-1, and diamide dilactam 10 were prepared, and their coronary vasodilator activity was assessed in dogs. Many compounds exhibited coronary vasodilator activity superior to that of fostedil. Among them, the 2-oxopyrrolidine derivative 7a was the most effective compound. Its action as a coronary vasodilator was 3 and 2 times more potent than that of fostedil and diltiazem hydrochloride, respectively.