Synthesis of 2-Phenylthiazolidine Derivatives as Cardiotonic Agents. I. 2-Phenylthiazolidine-3-thiocarboxamides

A series of novel 2-phenylthiazolidine-3-thiocarboxamides (II) was synthesized and tested for positive inotropic activity in the isolated guinea pig heart and in anesthetized dogs. Reaction of the benzaldehydes (VI, XI, XIV and XV) with cysteamine followed by treatment with isothiocyanates readily gave II. Structure-activity relationships were investigated by varying the structural parameters. N-Methyl-2 -phenylthiazolidine-3-thiocarboxamides having an ortho substituent such as a Me or OMe group exhibited significant positive inotropic action, which was not blocked by propranolol. Among the various ortho-alkoxyphenyl derivatives synthesized, the 2- (2- (3- (4-phenylpiperazino) propoxy) phenyl) derivative (I67) was found to exhibit more potent and longerlasting activity than amrinone without any significant effect on heart rate or blood pressure