Discovery of aryl-biphenyl-2-ylmethylpiperazines as novel scaffolds for 5-HT(7) ligands and role of the aromatic substituents in binding to the target receptor.

ABSTRACT

It has been reported that 5-HT(7) receptors are promising targets of depression and neuropathic pain. 5-HT(7) receptor antagonists have exhibited antidepressant-like profiles, while agonists have represented potential therapeutics for pain. In the course of our ongoing efforts to discover novel 5-HT(7) modulators, we designed an arylpiperazine scaffold with a substituted biphenyl-2-ylmethyl group. A series of biphenyl-2-yl-arylpiperazinylmethanes were then prepared, which showed a broad spectrum of binding affinities to the 5-HT(7) receptor depending upon the substituents attached to the biphenyl and aryl functionalities. Among those synthesized compounds, the compounds 1-24 and 1-26 showed the best binding affinities to the 5-HT(7) receptor with K(i) values of 43.0 and 46.0 nM, respectively. Structure-activity relationship study in conjunction with molecular docking study proposed that the 5-HT(7) receptor might have two distinctive hydrophobic binding sites, one specific for aromatic 2-OCH(3) substituents within the arylpiperazine and the other for biphenyl methoxy group.