Novel azido and isothiocyanato analogues of [3-(4-phenylalkylpiperazin-1- yl)propyl]bis(4-fluorophenyl)amines as potential irreversible ligands for the dopamine transporter

Potential irreversible ligands were prepared, based on a series of 3-(1-piperazinyl)propyl-N/N-bis(4-fluorophenyl)amines, as molecular probes for the dopamine transporter (DAT). Both azidoand isothiocyanato-substituted phenylalkyl analogues were synthesized and evaluated for displacement of [ ³H]WIN 35 428 in rat caudate putamen tissue. All of the analogues showed moderate binding potencies at the DAT. The azido analogue, 16b, was radioiodinated and used to photolabel human DAT-transfected HEK 293 cell membranes. [¹²⁵I]16b irreversibly labeled an ∼80 kDa band corresponding to the DAT detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This radioligand provides a novel addition to the growing arsenal of structurally diverse irreversible ligands that are being used to identify binding domains on the DAT. Characterizing points of attachment of these irreversible probes to the DAT protein will ultimately help elucidate the three-dimensional arrangement of the transmembrane domains, identify individual binding sites of the DAT inhibitors, and direct future drug design.