An efficient H 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 H-9 and H-9' (Δδ and Δδ), 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- d, methanol- d, or CDCl. 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.
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