S. Fazylov, O. Nurkenov, A. Arinova
Mar 1, 2016
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Chemistry of Natural Compounds
Abstract
1,3-Oxazolidine derivatives of ephedrine alkaloids are highly interesting because of their unique properties that allow them to be used in various practical medical and industrial applications and as enantioselective synthetic products of planar chiral compounds [1, 2]. The question of selective formation of oxazolidines has been noticed in the scientific literature. Different configurations of the chiral center in Dand L-ephedrines lead to different conformations for the 1,3-oxazolidine ring. The stereoselectivity of the reaction depends on the nature of the reactants and solvents. Many researchers [3–5] think that reactions of -aminoalcohols with various aldehydes in a nonpolar aprotic solvent, e.g., CHCl3 ( = 1.01 D), usually form the 2S-epimer or a mixture of isomers. Conversely, use of a protic polar solvent, e.g., MeOH ( = 1.71 D), favors formation of the 2R-stereoisomer. These reactions occur through intermediate iminium compounds (A and B) and involve the polar solvent.