SYNTHESIS OF ENANTIOMERICALLY PURE ALPHA-[C-14]METHYL-L-TRYPTOPHAN

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%.