A Pd-Mediated Approach to the Synthesis of an Unusual (beta)-Hydroxy­tryptophan Amino Acid Constituent of Cyclomarin A

A synthetic approach based on a palladium-mediated ­vinylation of indole derivatives was established for the preparation of 5, a key intermediate in the synthesis of N-(tert-butoxycarbonyl)-l-1H-[(R)-1,1-dimethyl-2,3-epoxypropyl]-(beta)-hydroxytryptophan ethyl ester (6). Unsatisfying yields were obtained using N-alkyl-3haloderivatives. The best method proved to be the oxidative coupling on 3-unsubstituted indole derivative.