Synthetic approaches to 9-arylated Cinchona alkaloids: stereoselective addition of Grignard reagents to cinchonanones and hydroxylation of 9-phenylcinchonanes
作者:Przemysław J. Boratyński、Ilona Turowska-Tyrk、Jacek Skarżewski
DOI:10.1016/j.tetasy.2012.05.024
日期:2012.6
All 8,9-isomers of the 9-phenyl Cinchona alkaloids were obtained by autoxidation of 9-deoxy-9-phenyl-alkaloids and by the addition of Grignard reagents to the respective ketones. The diastereoselective addition of phenyl-, methyl-, and vinylmagnesium reagents to quinidinone and cinchoninone gave the corresponding (8R,9S)-products with acceptable yields and starting material recovery. The configurations of the compounds obtained were established by chemical correlations, NMR experiments, and were supported by DFT calculations and X-ray structures. Stereochemical models for both reactions were also devised and discussed. (c) 2012 Elsevier Ltd. All rights reserved.