A three-step, highly enantioselective synthesis of (R)-2-methyl tryptophane ethyl ester: Comparison with chemical resolution

Article abstract of DOI:10.1016/S0040-4039(98)00633-9

(R)-2-Methyltryptophan ethyl ester, (R)-2, having an enantiomeric purity >,=96% was obtained in 3 steps and using (SSS)-hydroxypinanone, 1, as the recoverable chiral auxiliary. The synthesis of the alkylating agent, 5a, was improved (to a reproduceble 55% overall yield from 2,3-dimethylindole). The resolution of racemic-2 through chromatographic separation of the corresponding iminoester derived from (RRR)-1 also proved to be easy and efficient (-25% yield).