Synthesis and pharmacological evaluation of potent and enantioselective sigma-1 and sigma-2 ligands

In a previous study we found that substitutions of the (+)-cis-N-normetazocine nucleus of (+)-MPCB with 1-adamantanamine provide the compound (±)-10 with high affinity and selectivity for σ receptors. Starting with this result we have synthesized a new series of eight 1-phenyl-2-cyclopropylmethylamines structurally related to (±)-10, and binding affinities, with respect to σ1, σ2, opioid and dopaminergic D2 receptors, have been reported. All compounds showed a negligible opioid and dopaminergic affinity and high selectivity for σ receptors. Modifications on the amino moiety and methylcarboxyester group of 10 provide compounds with different σ1 and σ2 binding affinity and selectivity. Moreover, we have also synthesized the respective enantiomers of componds (±)-10 and (±)-18 in order to evaluate the enantioselectivity for σ1 and σ2 receptors. The binding data showed that carboxymethylester on the cyclopropane ring was more critical for enantioselectivity than the hydroxymethylenic group. In fact, the (−)-10 enantiomer showed a preference for σ1 whereas (+)-10 showed a preference for σ2.