Diastereoselective Rhodium-Catalyzed Ene-Cycloisomerization Reactions of Alkenylidenecyclopropanes: Total Synthesis of (−)-α-Kainic Acid
作者:P. Andrew Evans、Phillip A. Inglesby
DOI:10.1021/ja210804r
日期:2012.2.29
The rhodium-catalyzed ene-cycloisomerization of alkenylidenecyclopropanes provides an atom-economical approach to five-membered carbo- and heterocycles that contain two new stereogenic centers. A key and striking feature of this protocol is that the alkene geometry does not impact the efficiency and diastereocontrol, which provides excellent synthetic versatility. For instance, (E)- and (Z)-allylic
Both enantiomers of kainic acid have been synthesized from enantioenriched planar chiral cyclic amide 2a. The C3 and C4 stereocenters in the pyrrolidine ring were constructed by transannular Cope rearrangement of 2a, and the carboxyl group at the C2 position was introduced through lithiation followed by a carboxylation in the presence of an external chiral ligand.