Enantiospecific Synthesis of Optically Active 6-Methoxytryptophan Derivatives and Total Synthesis of Tryprostatin A1

Abstract

A concise preparation of optically active l or d-6-methoxytryptophan ethyl ester 21 was developed via the Fischer indole/Schöllkopf protocol from 6-methoxy-3-methylindole 16 (four steps, 58% overall yield). This method was extended to the enantiospecific total synthesis of tryprostatin A (11) via a regiospecific bromination process as a key step. In addition, 6-methoxy-2-bromotryptophan ethyl ester (32), a potential intermediate for indole alkaloid synthesis, was prepared via this strategy.