We report the
enantioselective total syntheses of mavacurans alkaloids, (+)-taberdivarine H, (+)-16-hydoxymethyl-pleiocarpamine,
(+)-16-epi-pleiocarpamine, and their postulated biosynthetic precursor
16-formyl-pleiocarpamine. This family of monoterpene indole alkaloids is a
target of choice since some of its members are subunits of intricate bisindole
alkaloids such as bipleiophylline. Inspired by the biosynthetic hypothesis, we
explored an oxidative coupling approach from the geissoschizine framework to
form the N1-C16 bond. Quaternization of the aliphatic nitrogen was key to achieve
the oxidative coupling induced by KHMDS/I<sub>2 </sub>since<sub> </sub>it hides
the nucleophilicity of the aliphatic nitrogen and locks the required cis conformation.
Bioinspired Oxidative Cyclization of the Geissoschizine Skeleton for the Enantioselective Total Synthesis of Mavacuran Alkaloids