Ring-substituted histaprodifen analogues as partial agonists for histamine H1 receptors: synthesis and structure–activity relationships
摘要:
Thirteen racemic benzene ring-substituted analogues of histaprodifen (8a; 2-[2-(3,3-diphenylpropyl)-1H-imidazol-4-yl]ethanamine), a novel lead for potent and selective histamine H-1-receptor agonists, have been prepared from substituted 4,4-diphenylbutyronitriles 5 via cyclization of the corresponding methyl butyrimidates 6 with 2-oxo-4-phthalimido-1-butyl acetate in liquid ammonia, followed by deprotection. Nitriles 5 were accessible by alkylation of either substituted diphenylmethanes with 3-bromopropionitrile or diethyl malonate with substituted 1-chloro-diphenylmethanes and subsequent standard reactions. The title compounds 8 displayed partial agonism on contractile H-1 receptors of the guinea-pig ileum (E-max = 2-98% relative to histamine) and, compared with the endogenous agonist, were endowed with agonist potencies of 4-92%. The meta fluorinated (gc) and meta chlorinated (8f) analogues showed the highest relative potency in this series (95% confidence Limits 85-99% and 78-102%), but did not exceed the value of the lead 8a (99-124%). Compound 8c (2-[2-[3-(3-fluorophenyl)-3-phenylpropyl]-1H-imidazol-4-yl]ethanamine) was a partial agonist at contractile H-1 receptors of the guinea-pig aorta (relative potency 154% vs. 100% for histamine) and at relaxation-mediating endothelial H-1 receptors of the rat aorta (relative potency 556% vs. 100% for histamine) and matched with the functional behaviour of 8a. Agonism observed for each compound was sensitive to blockade by the selective H-1-receptor antagonist mepyramine (pA(2) approximate to 9 (guinea-pig) and pA(2) approximate to 8 (rat aorta)). All histaprodifen analogues 8 stimulated neither histaminergic H-2/H-3, nor cholinergic M-3 receptors. They displayed only low to moderate affinity for these sites (H-2: pD'(2), < 5; H-3/M-3: pA(2) < 6). With regard to the substitution pattern on the benzene ring, there was no correlation between the histaprodifen series and the corresponding derivatives of another selective H-1-receptor agonist, viz. 2-phenylhistamine. (C) 2000 Editions scientifiques et medicales Elsevier SAS.
Ring-substituted histaprodifen analogues as partial agonists for histamine H1 receptors: synthesis and structure–activity relationships
摘要:
Thirteen racemic benzene ring-substituted analogues of histaprodifen (8a; 2-[2-(3,3-diphenylpropyl)-1H-imidazol-4-yl]ethanamine), a novel lead for potent and selective histamine H-1-receptor agonists, have been prepared from substituted 4,4-diphenylbutyronitriles 5 via cyclization of the corresponding methyl butyrimidates 6 with 2-oxo-4-phthalimido-1-butyl acetate in liquid ammonia, followed by deprotection. Nitriles 5 were accessible by alkylation of either substituted diphenylmethanes with 3-bromopropionitrile or diethyl malonate with substituted 1-chloro-diphenylmethanes and subsequent standard reactions. The title compounds 8 displayed partial agonism on contractile H-1 receptors of the guinea-pig ileum (E-max = 2-98% relative to histamine) and, compared with the endogenous agonist, were endowed with agonist potencies of 4-92%. The meta fluorinated (gc) and meta chlorinated (8f) analogues showed the highest relative potency in this series (95% confidence Limits 85-99% and 78-102%), but did not exceed the value of the lead 8a (99-124%). Compound 8c (2-[2-[3-(3-fluorophenyl)-3-phenylpropyl]-1H-imidazol-4-yl]ethanamine) was a partial agonist at contractile H-1 receptors of the guinea-pig aorta (relative potency 154% vs. 100% for histamine) and at relaxation-mediating endothelial H-1 receptors of the rat aorta (relative potency 556% vs. 100% for histamine) and matched with the functional behaviour of 8a. Agonism observed for each compound was sensitive to blockade by the selective H-1-receptor antagonist mepyramine (pA(2) approximate to 9 (guinea-pig) and pA(2) approximate to 8 (rat aorta)). All histaprodifen analogues 8 stimulated neither histaminergic H-2/H-3, nor cholinergic M-3 receptors. They displayed only low to moderate affinity for these sites (H-2: pD'(2), < 5; H-3/M-3: pA(2) < 6). With regard to the substitution pattern on the benzene ring, there was no correlation between the histaprodifen series and the corresponding derivatives of another selective H-1-receptor agonist, viz. 2-phenylhistamine. (C) 2000 Editions scientifiques et medicales Elsevier SAS.
Novel reductive Friedel-Crafts alkylation of aromatics catalyzed by indium compounds: Chemoselective utilization of carbonyl moieties as alkylating reagents
作者:Takashi Miyai、Yoshiyuki Onishi、Akio Baba
DOI:10.1016/s0040-4020(98)01130-2
日期:1999.1
Reductive Friedel-Crafts alkylation of aromatics with ketones or aldehydes was characteristically catalyzed by indium compounds in preference to general catalysts like AlCl3 and BF3, where hydrosilanes would play an important role both as a hydride donor and as a co-catalyst. Chemoselective utilization of ketone moieties as alkylating reagents took place even in the presence of halogen, ester or ether