Synthesis, σ receptor affinity, and pharmacological evaluation of 5-phenylsulfanyl- and 5-benzyl-substituted tetrahydro-2-benzazepines

Abstract

In accordance with a novel strategy for generating the 2-benzazepine scaffold by connecting C6-C1 and C3-N building blocks, a set of 5-phenylsulfanyl- and 5-benzyl-substituted tetrahydro-2-benzazepines was synthesized and pharmacologically evaluated. Key steps of the synthesis were the Heck reaction, the Stetter reaction, a reductive cyclization, and the introduction of diverse N substituents at the end of the synthesis. High σ1 affinity was achieved for 2-benzazepines with linear or branched alk(en)yl residues containing at least an n-butyl substructure. The butyl- and 4-fluorobenzyl-substituted derivatives, (±)-5-benzyl-2-butyl-2,3,4,5-tetrahydro-1H-2-benzazepine (19 b) and (±)-5-benzyl-2-(4-fluorobenzyl)-2,3,4,5-tetrahydro-1H-2-benzazepine (19 m), show high selectivity over more than 50 other relevant targets, including the σ2 subtype and various binding sites of the N-methyl-D-aspartate (NMDA) receptor. In the Irwin screen, 19 b and 19 m showed clean profiles without inducing considerable side effects. Compounds 19 b and 19 m did not reveal significant analgesic and cognition-enhancing activity. Compound 19 m did not have any antidepressant-like effects in mice.

Keywords: antidepressant activity; benzazepines; neuropathic pain; receptors; structure-activity relationships.