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

Abstract

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' (Δδ_H-9 and Δδ_H-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.