Organic Phosphorus Compounds. IV : Asymmetric 4-(Benzothiazol-2-yl)benxylphosphonates as Potent Calcium Antagonistic Vasodilators

Various asymmetric or cyclic ester derivatives of the phosphonic acid moiety in the calcium antagonist fostedil (KB-944) were synthesized. The coronary vasodilator activity of these compounds was assessed by Langendorff's method. Among them, the ethyl isopropyl ester 12 showed the most potent activity, which was comparable to that of fostedil.