An Efficient Method for Determining the Relative Configuration of Furofuran Lignans by 1H NMR Spectroscopy.

An efficient 1H NMR spectroscopic approach for determining the relative configurations of lignans with a 7,9':7',9-diepoxy moiety has been established. Using the chemical shift differences of H2-9 and H2-9' (ΔδH-9 and ΔδH-9'), the configurations of 8-H and 8-OH furofuran lignans can be rapidly and conveniently determined. The rule is applicable for data acquired in DMSO- d6, methanol- d4, or CDCl3. Notably, the rule should be applied carefully when the C-2 or C-6 substituent of the aromatic rings may alter the dominant conformers of the furofuran moiety.