Synthesis and biological evaluation of new non-imidazole H3-receptor antagonists of the 2-aminobenzimidazole series
作者:Mirko Rivara、Valentina Zuliani、Giuseppe Cocconcelli、Giovanni Morini、Mara Comini、Silvia Rivara、Marco Mor、Fabrizio Bordi、Elisabetta Barocelli、Vigilio Ballabeni、Simona Bertoni、Pier Vincenzo Plazzi
DOI:10.1016/j.bmc.2005.09.063
日期:2006.3
A novel series of non-imidazole H-3-receptor antagonists was developed, by chemical modification of a potent lead H-3-antagonist composed by an imidazole ring connected through an alkyl spacer to a 2-aminobenzimidazole moiety (e.g., 2-[[3-[4(5)-imidazolyl]propyl]amino]benzimidazole), previously reported by our research group. We investigated whether the removal of the imidazole ring could allow retaining high affinity for the H-3-receptor, thanks to the interactions undertaken by the 2-aminobenzimidazole moiety at the binding site. The imidazole ring of the lead was replaced by a basic piperidine or by a lipophilic p-chlorophenoxy substituent, modulating the spacer length from three to eight methylene groups; moreover, the substituents were moved to the 5(6) position of the benzimidazole nucleus. Within both the 2-alkylaminobenzimidazole series and the 5(6)-alkoxy-2-amino-benzimidazole one, the greatest H-3-receptor affinity was obtained for the piperidine-substituted compounds, while the presence of the p-chlorophenoxy group resulted in a drop in affinity. The optimal chain length was different in the two series. Even if the new compounds did not reach the high receptor affinity shown by the imidazole-containing lead compound, it was possible to get good H-3-antagonist potencies with 2-aminobenzimidazoles having a tertiary amino group at appropriate distance. (c) 2005 Elsevier Ltd. All rights reserved.