Synthesis and structure–activity relationships of N-(3-phenylpropyl)-N′-benzylpiperazines: Potent ligands for σ1 and σ2 receptors Original Research Article

Ten N-(3-phenylpropyl)-N′-benzylpiperazines having different substituents on the benzyl moiety were synthesized and evaluated for σ1 and σ2 receptor binding. The σ1 affinities were 0.37–2.80 nM, σ2 affinities were 1.03–34.3 nM, and selectivities, as σ2/σ1 affinity ratios, ranged from 1.4 to 52. Three compounds tested in a phenytoin shift binding assay profiled as probable σ1 antagonists. Quantitative structure–activity relationships depended on πx, MR or Es and Hammett σ values. The hydrophobicity term is negative for σ1 binding but positive for σ2 binding, indicating a major difference between the pharmacophores.