Synthesis of DL-[3-11C]phenylalanine

[3-11C]Phenylalanine has been prepared by a five-step synthesis beginning with 11CO2. [11C]Benzyl chloride was prepared by addition of 11CO2 to phenylmagnesium bromide, hydride reduction to [11C]benzyl alcohol, and chlorination (CCl4, tri-n-octylphosphine). The [11C]benzyl chloride was then used to alkylate the anion of N-diphenylmethylene)glycine ethyl ester using phase-transfer catalysis. The protecting groups were removed by acidic hydrolysis to yield DL-[3-11C]phenylalanine in 25-31% overall radiochemical yield (decay corrected) in a synthesis time of 60-70 min.