rotational population analysis
absolute configuration determination
nuclear magnetic resonance
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
A CD and 1H NMR study of the rotamer population around the C5-C6 bond of alkyl α-d-glucopyranosides proved it to be dependent on the aglycon and its absolute configuration, showing a similar, but not identical, behavior to that of their β-anomers. Thus, the population of the gt rotamer increased as the pKa of the aglycon increased, whereas the population of the tg and gg rotamers decreased, mainly that of the tg rotamer. The results showed the existence of a clear correlation between the stereoelectronic exo-anomeric effect and the rotamer distributions, the endo-anomeric effect not being directly involved. In addition, the 1H NMR chemical shift differences (δD-δROH) of the alkyl α-d-glucopyranosides are characteristic of the absolute configuration of the aglycon, as occurred with the β-anomers. Therefore, the absolute configuration of secondary chiral alcohols or the aglyconic moiety of natural glycosides can be determined independently of the anomeric configuration, a single enantiomer being sufficient. Chirality 9:626-637, 1997. © 1997 Wiley-Liss, Inc.
Type of Medium: