General Approach for the Synthesis of Sarpagine/Macroline Indole Alkaloids. Enantiospecific Total Synthesis of the Indole Alkaloid Trinervine

[structure: see text] The total synthesis of the indole alkaloid trinervine 1 was accomplished in enantiospecific fashion in an overall yield of 20% (from the tetracyclic ketone 8) in 10 reaction vessels (12.5% from tryptophan methyl ester). The synthesis of the N(a)-H substituted macroline equivalent 2 was also completed in high yield via the same intermediate 13. The unique protection/hydroboration process developed here should provide a method to functionalize the C(19)-C(20) double bond in similar systems.