Development of potent serotonin-3 (5-HT3) receptor antagonists. II. Structure-activity relationships of N-(1-benzyl-4-methylhexahydro-1H-1,4- diazepin-6-yl)carboxamides

Article abstract of DOI:10.1248/cpb.43.1912

Our studies on 4-amino-5-chloro-2-ethoxybenzamides led to the discovery that the N-(1,4-dimethylhexahydro-1H-1,4-diazepin-6-yl)benzamide 9 and the 1- benzyl-4-methylhexahydro-1H-1,4-diazepine analogue 10 are potent serotonin-3 (5-HT₃) receptor antagonists. Structure-activity relationship (SAR) studies on the influence of the aromatic nucleus of 9 and 10 upon inhibition of the von Bezold-Jarisch reflex in rats are described. Heteroaromatic rings such as pyrrole, thiophene, furan, pyridine, pyridaziae, 1,2-benzisoxazole, indole, quinoline, and isoquinoline rings showed weak 5-HT₃ receptor antagonistic activity. Within this series, use of the 1H-indazole ring as an aromatic moiety led to a substantial increase of the activity; the 1H- indazolylcarboxamides 54, 57, 97, and 102 showed potent 5-HT₃ receptor antagonistic activity. The optimal compound identified via extensive SAR studies was N-(1-benzyl-4-methylhexahydro-1H-1,4-diazepin-6-yl)-1H-indazole- 3-carboxamide (54), whose effect was superior to that of the corresponding benzamide 10 and essentially equipotent to those of ondansetron (1) and granisetron (4).

Full text of DOI:10.1248/cpb.43.1912

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