1,8-Naphthyridines VIII. Novel 5-aminoimidazo[1,2-a] [1,8]naphthyridine-6-carboxamide and 5-amino[1,2,4]triazolo[4,3-a] [1,8]naphthyridine-6-carboxamide derivatives showing potent analgesic or anti-inflammatory activity, respectively, and completely devoid of acute gastrolesivity.

On the basis of the very interesting pharmacological properties shown by the 5- amino[1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxamide derivatives 1, previously described by us, we have now prepared the 5-aminoimidazo[1,2-a][1,8]naphthyridine-6-carboxamide derivatives 2a–o (a new structural class) whose tricyclic system is isosteric to that of compounds 1. Both compounds 2 and some new properly substituted compounds 1 (1f–k) now synthesized were tested in vivo for their analgesic and antiinflammatory activities: on the whole, compounds 2 showed notable analgesic properties, whereas many compounds 1 exhibited a very potent antiinflammatory activity, coupled to scarce analgesic activity. All the effective compounds proved to be completely devoid of acute gastrolesivity (gastric damage) in rats (at the 200 mg kg_1 oral dose). European Journal of Medicinal Chemistry 45 (2010) 352–366