Entry into 6-Methoxy-D(+)-tryptophans. Stereospecific Synthesis of 1-Benzenesulfonyl-6-methoxy-D(+)-tryptophan Ethyl Ester

A strategy for the synthesis of optically active ring-A methoxylated indole alkaloids which employs the Moody azide/Schollkopf chiral auxiliary protocol has resulted in the successful preparation of 1-benzenesulfonyl-6-methoxy-D(+)-tryptophan ethyl ester 16. This amino ester is required for the synthesis of Alstonia bisindole alkaloids including macralstonine 2 via an enantiospecific Pictet-Spengler reaction.