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

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.