The stereochemistry of the tertiary hydroxyl group in diterpene furan glycosides viz. cordifolisides D (1) and cordifoliside E (2) has been assigned on the basis of pyridine
solvent induced shifts (PIS) in the 1H and 13C NMR spectra. The methyl and the methylene groups occupying positions vicinal, 1, 3-diaxial and geminal to the tertiary hydroxyl group
were deshielded to different extent depending on the dihedral angle. The stereochemical assignments are well supported by 13C-γ shifts and 2D Overhauser spectroscopy.
P. Pradhan, Gangan, V. D., Sipahimalani, A. T., and Banerji, A., “Stereochemical Assignment of Tertiary Hydroxyl Group in Diterpene Furan Glycosides by Pyridine Induced Shifts, 13C-and 2D-NMR Spectroscopy”, Spectroscopy letters, vol. 30, pp. 1467–1474, 1997.