文摘
The absolute configurations of 2-oxygenated phenylethanoid glycosides were conveniently determined by 1H NMR spectroscopy. A comparison of the chemical shift differences (Δδ) of the diastereotopic methylene protons (H-1) demonstrate that a large chemical shift difference corresponds to an R configuration and a small chemical shift difference indicates S for the 2-alkoxy form. However, the situation is contrary to that of the 2-hydroxy form. Furthermore, the mechanism underlying this result is discussed based on the visualized conformations of such compounds.