Nitrile analogs of meperidine as high affinity and selective sigma-1 receptor ligands

A series of N-substituted-4-cyano-4-phenylpiperidine analogs were synthesized and evaluated for binding affinity at opioid receptors and showed no affinity. The series similarity to previously reported sigma ligands prompted analysis at sigma receptors to determine the SAR for affinity at sigma receptors. Within the N-substituent series the saturated analogs showed increased affinity at both sigma receptors. Optimal chain length in the N-arylalkyl series for sigma(1) and sigma(2) receptors proved to be N-propylphenyl; extension to a four carbon chain dramatically decreased affinity at both receptors. Substituents in the 4-position affect only sigma(1) affinity; no change in affinity at sigma(2) was shown. The N-isobutyl, N-phenylpropyl, and N-benzyl analogs are worth pursuing due to their good affinity and selectivity at the sigma(1) receptor, whereas the N-benzyl analog exhibits the greatest selectivity for sigma(1).