s Asymmetric Synthesis of L-[3-13C]Tryptophan

Synthesis of L-[3-13C]tryptophan (2) from N,N-dimethyl[13C]formamide (4) and Dellaria's oxazinone 1 as a chiral glycine equivalent was achieved. Vilsmeier reaction of indole (5) and N,N-dimethyl[13C]formamide (4) afforded a good yield of indole-3-[13C]carbaldehyde (3), which was converted to the bromide 8. Diastereoselective alkylation of the enolate of 1 with the bromide 8 proceeded with high diastereoselectivity to give 9. Ethanolysis, hydrogenolysis and hydrolysis of 9 gave L-[3-13C]tryptophan (2).