ABSTRACT We report the total synthesis of (−)‐owerreine, a bis‐indole alkaloid biosynthetically assembled from two deoxoapodine units. This aspidosperma monomeric template was synthesized via a domino Michael/Mannich/ N ‐allylation sequence from a chiral indolyl‐ N ‐sulfinylimine and a DIAD‐oxidation‐promoted cycloetherification. It was further divergently transformed into an enamine precursor and an α,β−unsaturated indolenine, which were diastereoselectively assembled in the presence of the Eschenmoser salt through a 4+2 annulation. DFT calculations were deployed to gain insight into the mechanism and diastereoselectivity of this key step.
Coll et al. (Thu,) studied this question.