Synthesis of radiofluorinated analogs of m-tyrosine as potential l-dopa tracers via direct reaction with acetylhypofluorite

The direct electrophilic radiofluorination of m-tyrosine using [ 18F]acetylhypofluorite was investigated. Results showed that this reaction was both rapid and efficient with recovered decay corrected yield of 71% radiofluorinated m-tyrosines based on starting [ 18F]acetylhypofluorite. Specific activity of the product obtained in this study was 100–200 mCi/mmol although 1–5 Ci/mmol are easily achievable with our improved production of [ 18F]AcOF. Three positional isomers were found and identified by 19F-NMR to be 2-, 4-, 6-fluoro- m-tyrosine with a distribution of 36:11:52, respectively. This measured distribution allowed the assignment of the radio-HPLC peaks. Biological studies are currently underway in our laboratory using these fluoro- m-tyrosines to determine which isomer would be most suited for the evaluation of the dopamine system by positron tomography.