A practical method for the preparation of large amounts of enantiomeri
cally pure alpha-[C-14]methyl-L-tryptophan using the enzymatic resolut
ion of the corresponding D,L-Methyl ester is reported. The radiolabell
ed alpha-methyl group was introduced using the alpha-methylation of th
e lithium enolate of the Schiff base Of L-tryptophan methyl ester. Hyd
rolysis of the Schiff base with 1 N HCl provided the D,L-methyl ester
of alpha-[C-14]methyl tryptophan. Enantioselective enzymatic hydrolysi
s of the L-methyl ester by alpha-chymotrypsin gave the enantiomericall
y pure alpha-[C-14]methyl-L-tryptophan. The overall yield of this prep
aration was 33%.