2-Aryl-substituted,benzo-anellated 5-membered heterocyclic compounds as potentially active substances for the cardiovascular system: 1,3-Benzothiazolyl- and 1,3-benzoxazolylbenzylphosphonates

In the course of investigations on structure-activity relationships of calcium antagonists analogous to fostedil, a series of 2-aryl- and 2-arylvinyl-substituted 1,3-henzothiazoles and 1,3-benzoxazoles bearing a phosphonate group on the phenyl ring has been synthesized by cyclization, bromination, and subsequent Michaelis-Arbuzow reaction. Pharmacological investigations on isolated organs from guinea pigs revealed both negative inotropic effects and a relaxing action on smooth musculature; these activities were particularly pronounced in the 1,3-benzothiazole compound group.