Regio- and diastereoselective functionalization of (−)-cytisine: an unusual N–C acyl migration
作者:Jacques Rouden、Alexis Ragot、Sonia Gouault、Dominique Cahard、Jean-Christophe Plaquevent、Marie-Claire Lasne
DOI:10.1016/s0957-4166(02)00271-9
日期:2002.7
In order to test (-)-cytisine as a potential chiral inductor, N-propionyl cytisine was treated with LDA and then with benzyl bromide. Instead of the expected alpha-benzyl substituted propionamide, (-)-N-benzyl 6alpha-propionyl cytisine was formed, arising from an unusual diastereoselective nitrogen to carbon acyl migration. Using LDA in the presence of an excess of LiCl, the 6-substituted cytisine was isolated in yields of up to 79%. The efficiency of the N-C acyl transfer was shown to be dependent on the nature of the N-acyl group. Complete epimerization of the newly created stereocenter was observed under basic conditions. This methodology allows the stereoelective functionalization of the C-6 position of cytisine, an important agonist of nicotinic receptors. (C) 2002 Elsevier Science Ltd. All rights reserved.