Development of high-affinity 5-HT3 receptor antagonists. 2. Two novel tricyclic benzamides

Abstract

Two new classes of potent 5-HT3 agents have been developed and examined as inhibitors of cytotoxic drug induced emesis in the ferret and dog. The absolute configuration of the most active molecules 10 and 18 have been determined by X-ray crystallography. These two compounds are more potent than known 5-HT3 receptor antagonists both in vivo and in vitro in blocking 5-HT3 receptor activation and preventing chemotherapeutic induced emesis. Compared with 5-HT3 antagonists, such as GR 38032F, zacopride, BRL 43694, and ICS 205-930, compound 10 was more potent in (1) inhibiting binding to 5-HT3 receptor binding sites in rat cortex (Ki = 0.17 nM), (2) blocking the von Bezold-Jarisch effect in the rat (lowest effective dose, 1 microgram/kg iv), and (3) inhibiting 5-HT-induced contraction of guinea pig ileum (lowest effective concentration, 10(-9) M). This novel agent was as effective given po as when given iv in reducing cisplatin-induced emetic episodes in the ferret (ED50 = 4 micrograms/kg iv or po). A 1 mg/kg po dose of 10 virtually abolished cisplatin-induced emesis for 10 h in the ferret. However, it was inactive against apomorphine or copper sulfate-induced vomiting. These data, coupled with receptor binding studies of ligands for D2-dopamine, a1, a2, 5-HT1, 5-HT2, and muscarinic receptors demonstrate that 10 is a highly selective 5-HT3 receptor antagonist with remarkable potency in vivo.

Efficient Synthesis of Furan-2-ylacetates, 7-(Alkoxycarbonyl)benzofurans, and 7-(Alkoxycarbonyl)-2,3-dihydrobenzofurans Based on Cyclization Reactions of Free and Masked Dianions: A “Cyclization/Dehydrogenation” Strategy

“…So far, dehydrogenation reactions have been rarely used for the synthesis of furans and benzofurans. For example, 2,3-dihydrobenzofurans have been transformed into benzofurans by dehydrogenation . The dehydrogenation of tetrahydrofurans and 2,3,4,5,6,7-hexahydrobenzofurans has been reported to give furans and benzofurans, respectively .…”

Vibrational spectra, NBO, HOMO–LUMO and conformational stability studies of 4-hydroxythiobenzamide

“…ichthyosis and psoriasis as well as in the treatment of fungal skin infections such as tinea [1][2][3][4][5][6][7][8]. 4-Hydroxythiobenzamide is the most popular model systems for studying intramolecular hydrogen bonds [9][10].…”