FURTHER INVESTIGATION ON THE RADIOSYNTHESIS OF ALPHA-[C-11]METHYL-TRYPTOPHAN

Improved procedures for the radiosynthesis of alpha-[C-11]methyltryptophan and alpha-[C-11]methyl-tryptophan methyl ester were studied. Following alpha-deprotonation of tryptophan methyl ester benzaldimine with LDA, 60-80% of no carrier added [C-11]iodomethane was incorporated in 5 minutes at 27-30-degrees-C. After HPLC purification, radiochemically pure alpha-[C-11]methyl-tryptophan or its methyl ester was produced with minimum chemical contamination from tryptophan. The [C-11]methyl-tryptophan synthesized, however, was found to be a racemate.