Discovery of novel conformationally constrained tropane-based biaryl and arylacetylene ligands as potent and selective norepinephrine transporter inhibitors and potential antidepressants

To further explore the structure–activity relationships of conformationally constrained tropanes, a number of new biaryl and arylacetylene analogs were designed and synthesized. Some of these compounds such as 3a–b, 3d, 3f–h, 5b, and 7g were found to be highly potent and selective or mixed norepinephrine transporter (NET) inhibitors with Ki values of 0.8–9.4 nM. Moreover, all of these compounds display weak to extremely weak muscarinic receptor binding affinity, indicating that as potential antidepressants, they may overcome certain side effects that are of concern with other antidepressants, which are thought to be mediated by their anticholinergic properties.