Polycyclic N‐hetero compounds. XLIII. Syntheses and properties of 2‐substituted 1‐acetoxy‐6‐acetyl‐5,6‐dihydro‐4H‐imidazo[1′,2′:1,6]‐pyrimido[5,4‐d][1]benzazepines viaN‐(6,7‐dihydro‐5H‐pyrimido[5,4‐d]‐[1]benzazepin‐4‐yl)amino acids and their analogous mesoionic compounds, and their related compounds as a series of potential blood platelet aggregation inhibitors

A study of the cyclization method by heating of N‐(6,7‐dihydro‐5H‐pyrimido[5,4‐d][1]benzazepin‐4‐yl)amino acids 3a‐h, 6, and 9a,b with excess acetic anhydride for the preparation of 2‐substituted 1‐acetoxy‐6‐acetyl‐5,6‐dihydro‐4H‐imidazo[1,2′:1,6]pyrirnido[5,4‐d][1]benzazepines 4a‐h and tetra‐ and penta‐cyclic mesoionic compounds 7 and 10a,b has been made. In addition, a tetracyclic mesoionic compound having a sulfur atom on the skeleton, 5,6‐dihydro‐4H‐thiazolo[3′,2′:1,6]pyrimido[5,4‐d][1]benzazepiniurn‐1‐one (12) was similarly prepared by treatment of 2‐(6,7‐dihydro‐5H‐pyrimido[5,4‐d][1]benzazepm‐4‐ylthio)acetic acid (11) with excess acetic anhydride. Their inhibitory activities against collagen‐induced aggregation of rabbit blood platelets in vitro were also investigated, and some heterocycles exhibited from a two‐ to a four‐fold more potent activity as compared with aspirin.