Antivertigo Agents. IV. Synthesis and Antivertigo Activity of 6-[ω-(4-Aryl-1-piperazinyl) alkyl]-5, 6, 7, 8-tetrahydro-1, 6-naphthyridines

A series of novel 6-[ω-(4-aryl-1-piperazinyl) alkyl]-5, 6, 7, 8-tetrahydro-1, 6-naphthyridines was synthesized and evaluated for antivertigo activity by testing their ability to inhibit spontaneous nystagmus in cats. Structure-activity relationships are discussed. Many of the compounds having the 4-(2-alkoxyphenyl) piperazine group as the 4-arylpiperazine moiety showed more potent antivertigo activity than diphenidol. Among them, 2-{2-[4-(2-ethoxyphenyl)-1-piperazinyl] ethyl}-1, 2, 3, 4, 6, 7, 8, 9-octahydrobenzo [b] [1, 6] naphthyridine (NK 422, 41) was selected as a promising antivertigo agent. NK 422 also exhibited a more potent inhibitory effect on apomorphine-induced vomiting in dogs than diphenidol.