New 5-HT₃ (Serotonin-3) Receptor Antagonists. I. Synthesis and Structure-Activity Relationships of Pyrido[1, 2-α]indoles

抄録

A series of pyrido[1, 2-α]indol-6(7H)-ones was prepared and evaluated for 5-HT₃ receptor antagonist activity. The structural requirements for the 5-HT₃ receptor antagonist have been defined as an aromatic moiety, a basic nitrogen, and a linking acyl group. The (5-methylimidazol-4-yl)methyl group as a basic nitrogen moiety was an important element for high potency. The highest potency was observed for compounds which have 7- and 10-methyl substituents on the pyrido[1, 2-α]indol-6(7H)-one ring. From this series, (+)-11b (FK 1052) was selected for further evaluation. FK 1052 was a potent 5-HT₃ receptor antagonist in the Bezold-Jarisch reflex test in rats (ED₅₀ 0.9 μg/kg, i.v.) and a very effective antiemetic agent against cisplatin-induced emesis in dogs (ED₅₀ 1.1×2 μg/kg, i.v. and 2.7×2 μg/kg, p.o.).