Determination of the absolute configuration of sulfinyl glycosides: the role of the exo-anomeric effect

The diastereoselective synthesis and conformational study of alpha- and bet a -ethylsulfinylglycosides have been studied. It was found that while beta- (S-S)-sulfinyl glycosides are flexible beta-(R-S)-sulfinyl glycosides exist s in a major conformation stabilized by the exo-anomeric effect. The genera lity of the hyperconjugative delocalisation gives rise to a general rule fo r the determination of the absolute configuration of sulfinyl glycosides by H-1 or C-13 NMR spectroscopy without need of chemical shift reagents. (C) 2000 Published by Elsevier Science Ltd.