Quinazoline derivatives and their pharmaceutically acceptable acid addition salts having the general formula ##STR1## wherein R.sup.1 and R.sup.2 each represents hydrogen or alkyl; R.sup.3 represents alkyl or substituted alkyl; R.sup.7 and R.sup.8 each represent alkoxy; Z is oxygen or sulfur; m is zero or 1; n is zero or an integer from 1 to 5, exhibit a cardiotonic activity with little tendency to cause tachycardia.
Studies on cardiotonic agents. IV. Synthesis of novel 1-(6,7-dimethoxy-4-quinazolinyl)piperidine derivatives carrying substituted hydantoin and 2-thiohydantoin rings.
7-dimethoxy-4-quinazolinyl)piperidines carrying substituted hydantoin and 2-thiohydantoin rings was synthesized and examined for cardiotonic activity in anesthetized dogs. Introduction of isopropyl and sec-butyl group at the 5-position of the hydantoin and thiohydantoin rings led to potent inotropic activity. Effects of insertion of an alkyl chain between the piperidine and the hydantoin rings were