Synthesis and Structure−Activity Relationships of a New Model of Arylpiperazines. 1. 2-[[4-(<i>o</i>-Methoxyphenyl)piperazin-1-yl]methyl]-1,3- dioxoperhydroimidazo[1,5-<i>a</i>]pyridine:  A Selective 5-HT_1A Receptor Agonist

Abstract

A series of new bicyclohydantoin-arylpiperazines was prepared and evaluated for affinity at 5-HT1A, alpha 1, and D2 receptors. Most of the compounds showed very low affinity for D2 receptors, and most of them demonstrated moderate to high affinity for 5-HT1A and alpha 1 receptor binding sites. SAR observations indicated that the length of the alkyl chain between the arylpiperazine and the hydantoin moiety is of great importance for 5-HT1A/alpha 1 affinity and selectivity, n = 1 being the optimal value. Compound 1h, 2-[[4-(o-methoxyphenyl)piperazin-1-yl] methyl]-1,3-dioxoperhydroimidazo [1,5-alpha]pyridine, bound at 5-HT1A sites with nanomolar affinity (Ki = 31.7 nM) and high selectivity over alpha 1, D2, and 5-HT2A receptors (Ki > 1000, > 10 000, and > 1000 nM, respectively). Preliminary studies showed that this agent is probably functioning as a partial to full 5-HT1A agonist, and it displayed anxiolytic activity on the social interaction test in mice.