Platelet aggregation inhibitors

A method of treating a mammal to inhibit platelet aggregation comprising administering a therapeutically effective amount of a compound of the formula ##STR21## or a pharmaceutically acceptable salt thereof wherein Z is selected from the group consisting of H, halogen, hydroxy, alkoxy of from one to six carbon atoms and alkyl of from one to six carbon atoms;

• wherein A is selected from the group consisting of alkyl of one to six carbon atoms, alkenyl of two to six carbon atoms and alkynyl of two to six carbon atoms;
• wherein R.sub.1 is selected from the group consisting of H, alkyl of from one to six carbon atoms, aralkyl and alkanoyloxyalkyl;
• and
• wherein R.sub.2 is selected from the group consisting of H, alkyl of from one to six carbon atoms, alkenyl of from two to six carbon atoms, alkynyl of from two to six carbon atoms, aryl and heteroaryl wherein the heteroatom is nitrogen optionally substituted by a radical selected from the group consisting of halogen, alkyl of one to six carbon atoms, alkoxy of one to six carbon atoms, carboxyl derivatives, nitro, cyano, azido, ureido, ureylene, alkoxycarbonyloxy, hydroxyl, alkylamino, alkoxycarbonyl, trialkylsilyl, alkoxyimino, alkylsulfonyl, phenylsulfonyl and amino.