Investigations on the 1-(2-Biphenyl)piperazine Motif: Identification of New Potent and Selective Ligands for the Serotonin7 (5-HT7) Receptor with Agonist or Antagonist Action in Vitro or ex Vivo

Here we report the design, synthesis, and 5-HT7 receptor affinity of a set of 1-(3-biphenyl)- and 1-(2-biphenyl)piperazines. The effect on 5-HT7 affinity of various substituents on the second (distal) phenyl ring was analyzed. Several compounds showed 5-HT7 affinities in the nanomolar range and >100-fold selectivity over 5-HT1A and adrenergic α1 receptors. 1-[2-(4-Methoxyphenyl)phenyl]piperazine (9a) showed 5-HT7 agonist properties in a guinea pig ileum assay but blocked 5-HT-mediated cAMP accumulation in 5-HT7-expressing HeLa cells.