by Barry M. Trost*, Dustin A. Bringley, Ting Zhang
and Nicolai Cramer
The marcfortines are complex secondary
metabolites that show potent anthelmintic activity and are characterized by the
presence of a bicyclo[2.2.2]diazaoctane fused to a spirooxindole. Herein, we
report the synthesis of two members of this family. The synthesis of
marcfortine B utilizes a carboxylative TMM cycloaddition to establish the
spirocyclic core, followed by an intramolecular Michael addition and oxidative
radical cyclization to access the strained bicyclic ring system. In addition,
the first asymmetric synthesis of (−)-marcfortine C is described. The key step
involves a cyano-substituted TMM cycloaddition, which proceeds in nearly
quantitative yield with high diastereo- and enantioselectivity. The resulting
chiral center was used to establish all remaining stereocenters in the natural
product.
Journal of the American Chemical Society
Publication Date (Web): October 1, 2013
No comments:
Post a Comment