Stereoselective C9 Arylation and Vinylation of Cinchona Alkaloids
摘要:
A simple and efficient method for the highly stereoselective C-9 arylation and vinylation of Cinchona alkaloids was developed. Both 9s- and 9R-chloroquinine with PhMgBr yielded 9S-phenylquinine (X-ray structure). The reactions with various aryl and vinyl Grignard reagents resulted in the series of 9S-aryl and vinyl alkaloid derivatives. The stereochemical outcome was rationalized by coordination of the magnesium atom to the quinuclidine nitrogen, thus directing the nucleophilic attack at the C-9 stereogenic center.
Long-standing errors of the supposedly established literature, including textbooks and data bases have been corrected: The structure of the hetero-cinchona bases in the crystal and in solution (see scheme) and the mechanism of their formation from quinine and quinidine have been elucidated.
Stereoselective C9 Arylation and Vinylation of <i>Cinchona</i> Alkaloids
作者:Przemysław J. Boratyński、Ilona Turowska-Tyrk、Jacek Skarżewski
DOI:10.1021/ol7026625
日期:2008.2.1
A simple and efficient method for the highly stereoselective C-9 arylation and vinylation of Cinchona alkaloids was developed. Both 9s- and 9R-chloroquinine with PhMgBr yielded 9S-phenylquinine (X-ray structure). The reactions with various aryl and vinyl Grignard reagents resulted in the series of 9S-aryl and vinyl alkaloid derivatives. The stereochemical outcome was rationalized by coordination of the magnesium atom to the quinuclidine nitrogen, thus directing the nucleophilic attack at the C-9 stereogenic center.