Efficient automated syntheses of high specific activity 6-[18F]fluorodopamine using a diaryliodonium salt precursor.

6-[(18)F]Fluorodopamine (6-[(18) F]F-DA) is a positron emission tomography radiopharmaceutical used to image sympathetic cardiac innervation and neuroendocrine tumors. Imaging with 6-[(18)F]F-DA is constrained, in part, by the bioactivity and neurotoxicity of 6-[(19)F]fluorodopamine. Furthermore, routine access to this radiotracer is limited by the inherent difficulty of incorporation of [(18)F]fluoride into electron-rich aromatic substrates. We describe the simple and direct preparation of high specific activity (SA) 6-[(18)F]F-DA from no-carrier-added (n.c.a.) [(18)F]fluoride. Incorporation of n.c.a. [(18)F]fluoride into a diaryliodonium salt precursor was achieved in 50-75% radiochemical yields (decay corrected to end of bombardment). Synthesis of 6-[(18)F]F-DA on the IBA Synthera® and GE TRACERlab FX-FN automated platforms gave 6-[(18)F]F-DA in >99% chemical and radiochemical purities after HPLC purification. The final non-corrected yields of 6-[(18)F]F-DA were 25 ± 4% (n = 4, 65 min) and 31 ± 6% (n = 3, 75 min) using the Synthera and TRACERlab modules, respectively. Efficient access to high SA 6-[(18)F]F-DA from a diaryliodonium salt precursor and n.c.a. [(18)F]fluoride is provided by a relatively subtle change in reaction conditions - replacement of a polar aprotic solvent (acetonitrile) with a relatively nonpolar solvent (toluene) during the critical radiofluorination reaction. Implementation of this process on common radiochemistry platforms should make 6-[(18)F]F-DA readily available to the wider imaging community.