First Enantiospecific Total Synthesis of the Important Biogenetic Intermediates, (+)-Polyneuridine and (+)-Polyneuridine Aldehyde, as Well as 16-Epi-vellosimine and Macusine A

The first enantiospecific total synthesis of the alkaloids 16-epi-vellosimine (1), (+)-polyneuridine (2), (+)-polyneuridine aldehyde (3), and macusine A (4) is reported. The key oxidation was accomplished with the Corey-Kim reagent to provide the important biogenetic intermediates, 16-epi-vellosimine (1) and polyneuridine aldehyde (3), the latter of which is required for the conversion of the sarpagan skeleton into the ajmalan system in the biosynthesis of quebrachidine. [reaction: see text].