HIGH-YIELD SYNTHESIS OF HIGH SPECIFIC ACTIVITY R-(-)-[C-11]EPINEPHRINE FOR ROUTINE PET STUDIES IN HUMANS

R-(-)-[C-11]Epinephrine ([C-11]EPI) has been synthesized from R-(-)-norepinephrine by direct methylation with [C-11]methyl iodide or [C-11]methyl triflate. The total synthesis time including HPLC purification was 35-40 min. The radiochemical yields (EOB) were 5-10% for [C-11]methyl iodide and 15-25% for [C-11]methyl triflate. Radiochemical purity was >98%; optical purity determined by radio-chiral HPLC was >97%. The [C-11]methyl triflate technique produces R-(-)-[C-11]epinephrine in quantities (80-170 mCi) sufficient for multiple positron emission tomography studies in humans. The two synthetic methods are generally applicable to the production of other N-[C-11]methyl phenolamines and N-[C-11]methyl catecholamines.