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-(-)-no repinephrine by direct methylation with [C-11]methyl iodide or [C-11]m ethyl triflate. The total synthesis time including HPLC purification w as 35-40 min. The radiochemical yields (EOB) were 5-10% for [C-11]meth yl iodide and 15-25% for [C-11]methyl triflate. Radiochemical purity w as >98%; optical purity determined by radio-chiral HPLC was >97%. The [C-11]methyl triflate technique produces R-(-)-[C-11]epinephrine in qu antities (80-170 mCi) sufficient for multiple positron emission tomogr aphy studies in humans. The two synthetic methods are generally applic able to the production of other N-[C-11]methyl phenolamines and N-[C-1 1]methyl catecholamines.