Alternative solvents for electrophilic synthesis of 6-[18F]fluoro-L-DOPA

Owing to the ozone layer-depleting properties of chlorofluorocarbon compounds, alternative solvents for electrophilic fluorination reactions are desirable. Chloroform, dichloromethane, acetone or their deuterated analogues were examined as substitutes for Freon-11 in the electrophilic synthesis of 6-[F-18]fluoro-L-DOPA ([F-18]FDOPA). CDCl3, CD2Cl2 and C3D6O were found to be suitable solvents in this reaction, with the deuterated solvents providing significantly higher yields than Freon-11. There were no differences among the solvents in the specific radioactivity, the radiochemical purity, the chemical purity or the microbiological quality of the final product. However, the radiochemical yield of [F-18]FDOPA was increased when acetic acid was added to the precursor solution prior to the fluorination reaction.