Enantiospecific total synthesis of the enantiomer of the indole alkaloid intermediate macroline

The total synthesis of the enantiomer 3En of macroline 3 was completed (from l-tryptophan methyl ester 6) in an overall yield of 12.3% (11 isolated intermediates). The corresponding macroline equivalent 18 was prepared in 14.3% yield. This work provides, for the first time, an opportunity to synthesize mismatched bisindole alkaloids for studies on the mechanism of action of Alstonia antimalarial alkaloids at the receptor level.