Enantioselective synthesis of 11C-labeled phenylethanolamine

No-carrier-added [1-11C]phenylethanolamine was prepared by the oxynitrilase-catalyzed addition of hydrogen [11C]cyanide to benzaldehyde followed by reduction of the [11C]cyanohydrin. Radiochemical yields of 2-4% at end-of-synthesis were obtained in a preparation time of 50-60 min from the end of hydrogen [11C]cyanide production. The enantiomeric composition was determined through its conversion to the diastereomeric Mosher amide-esters; the enantiomeric purity of the [11C]phenylethanolamine produced via NaBH4CoCl2 reduction was 60% e.e. (R/S = 80/20) while that prepared through boran-THF complex reduction was 80% e.e. (R/S = 90/10). (author)