Irreversible binding of a novel phenylisothiocyanate tropane analog to monoamine transporters in rat brain

Azido-iodo-N-benzyl derivatives of threo-methylphenidate (Ritalin, Concerta): Rational design, synthesis, pharmacological evaluation, and dopamine transporter photoaffinity labeling

In contrast to tropane-based compounds such as benztropine and cocaine, non-tropane-based photoaffinity ligands for the dopamine transporter (DAT) are relatively unexplored. Towards addressing this knowledge gap, ligands were synthesized in which the piperidine nitrogen of 3- and 4-iodomethylphenidate was substituted with a benzyl group bearing a photoreactive azide. Analog (±)-3a demonstrated modest DAT affinity and a radioiodinated version was shown to bind covalently to rat striatal DAT and hDAT expressed in cultured cells. Co-incubation of (±)-3a with nonradioactive d-(+)-methylphenidate or (-)-2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane (β-CFT, WIN-35,428, a cocaine analog) blocked DAT labeling. Compound (±)-3a represents the first successful example of a DAT photoaffinity ligand based on the methylphenidate scaffold. Such ligands are expected to assist in mapping non-tropane ligand-binding pockets within plasma membrane monoamine transporters.

A novel photoaffinity ligand for the dopamine transporter based on pyrovalerone

Non-tropane-based photoaffinity ligands for the dopamine transporter (DAT) are relatively unexplored in contrast to tropane-based compounds such as cocaine. In order to fill this knowledge gap, a ligand was synthesized in which the aromatic ring of pyrovalerone was substituted with a photoreactive azido group. The analog 1-(4-azido-3-iodophenyl)-2-pyrrolidin-1-yl-pentan-1-one demonstrated appreciable binding affinity for the DAT (K(i)=78+/-18 nM), suggesting the potential utility of a radioiodinated version in structure-function studies of this protein.