Highly selective, novel analogs of 4-[2-(diphenylmethoxy)ethyl]- 1-benzylpiperidine for the dopamine transporter: effect of different aromatic substitutions on their affinity and selectivity.

Several analogs of the potent and selective dopamine transporter (DAT) ligand 4-[2-(diphenylmethoxy)ethyl]-1-benzylpiperidine, 1a, were prepared and biologically evaluated at the dopamine and serotonin transporter (SERT) sites. Several substituents were introduced in the aromatic rings to evaluate the influences of electronic and steric interactions in their binding to the DAT. All the novel analogs showed preferential interaction at the DAT compared with the SERT. Different aromatic substitutions in the phenyl ring of the N-benzyl part of the molecule played a key role in the selectivity. In general, compounds with strong electron-withdrawing substituents were most active and selective at the DAT. Thus, compounds 5a (R = F) and 11b (R = NO2) were among the most potent (IC50 = 17.2 and 16.4 nM, respectively) and most selective (SERT/DAT = 112 and 108, respectively) and were far more selective than GBR 12909 (SERT/DAT = 6). Bioisosteric replacement of one of the phenyl rings of the diphenylmethoxy moiety by a thiophene ring was tolerated well and produced the most potent compound 13b (IC50 = 13.8 nM) in the series. Our current structure-activity studies of these piperidine analogs resulted in the generation of second generation of GBR-type compounds, and all of these new compounds reported here were more selective than GBR 12909 in interacting with the DAT over the SERT.