The enantioselective Birch-Cope sequence for the synthesis of carbocyclic quaternary stereocenters. Application to the synthesis of (+)-mesembrine.
A synthetic technique for generating carbocyclic quaternary stereocenters with exceptionally high levels of enantioselectivity is described. A sequence of three reactions, enantioselective Birch reduction-allylation, enol ether hydrolysis, and Cope rearrangement, is used to stereoselectively generate chiral quaternary centers on a 2-cyclohexen-1-one ring. The products of the sequence are 4,4-disubstituted-2-carboxamide-2-cyclohexen-1-one structures which are versatile intermediates in complex natural product synthesis. An application of the sequence to the synthesis of (+)-mesembrine illustrates the utility of these intermediates.
Paul
Tapas
T
Department of Chemistry, Bryn Mawr College, Bryn Mawr, PA 19010-2899, USA.
Malachowski
William P
WP
Lee
Jisun
J