TETRA-O-BENZOYLGLUCOSYLATION - A NEW H-1 NUCLEAR-MAGNETIC-RESONANCE METHOD FOR DETERMINATION OF THE ABSOLUTE-CONFIGURATION OF SECONDARY ALCOHOLS

A new method for determination of the absolute configuration of secondary alcohols based on the anisotropic effect and glycosylation-induced H-1 NMR shifts is described. The tetra-O-benzoyl-beta-glucosylation of secondary alcohols induces dramatic shifts in the aglycon H-1 NMR peaks. The differences between the proton chemical shifts of the D-glucosylated derivative and the free alcohol (Delta delta = delta(D) - delta(ROH)) or more significantly between their chemical shifts in the D- and L-glucosylated derivatives (Delta delta = delta(D) - delta(L)) are characteristic of the absolute configuration of the secondary chiral alcohol. Furthermore, in most cases the sign of the chemical shift difference of the carbinyl protons correlates with the absolute configuration of their carbons, namely positive or negative Delta delta are obtained for (R)- or (S)-carbinyl carbons, respectively. Moreover, this method involves the use of one enantiomer and generally a single derivatization is sufficient.