Structural analogues of 5-OMe-BPAT:: Synthesis and interactions with dopamine D2, D3, and serotonin 5-HT1A receptors

Several structural analogues of 5-methoxy-2-[N-(2-benzamidoethyl)-N-n-propylamino]tetralin (5-OMe-BPAT, 1), a representative of a series of 2-aminotetralin-derived benzamides with po ten tial atypical antipsychotic properties, were synthesized and evaluated for their ability to bind to dopamine D-2A, D-3, and serotonin 5-HT1A receptors in vitro. The structure-affinity relationships revealed that the aromatic ring of the benzamide moiety of 1 contributes to the high affinities for all three receptor subtypes. Furthermore, 1 may interact with the dopamine D-2 and D-3 receptors through hydrogen bond formation with its carbonyl group. Investigation of the role of the amide hydrogen atom by amide N-alkylation was not conclusive, since conformational aspects may be responsible for the decreased dopaminergic affinities of the N'-alkylated analogues of 1. The effects of the amide modifications on the serotonin 5-HT1A receptor affinity were less pronounced, suggesting that the benzamidoethyl side-chain of 1 as a whole enhances the affinity for this receptor subtype probably through hydrophobic interactions with an accessory binding site. The structural requirements for the substituents at the basic nitrogen atom supported the hypothesis that the 2-aminotetralin moieties of the 2-aminotetralin-derived substituted benzamides may share the same binding sites as the 2-(N, N-di-n-propylamino)tetralins. (C) 1999 Elsevier Science Ltd. All rights reserved.