Reinvestigation of the Stereochemistry of the C-Glycosidic Ellagitannins, Vescalagin and Castalagin

The stereochemistry of the C-glycosidic ellagitannins, vescalagin and castalagin, has been reinvestigated using computational methods. DFT calculations of their H-1 and C-13 NMR spectra, as well as TDDFT calculations of the ECD spectra of their des-hexahydroxydiphenoyl analogues, revealed that the structure of the triphenoyl moiety of vescalagin and castalagin should be revised.