Distribution of erythro and threo forms of different types of β‐O‐4 structures in aspen lignin by 13C NMR using the 2D INADEQUATE experiment

Abstract

Carbon–carbon connectivity spectra of 13C-enriched aspen lignin recorded using the 2D INADEQUATE experiment revealed cross peaks which can be assigned to four types of arylglycerol β-aryl ethers (β-O-4 structures): erythro forms of arylglycerol β-syringyl ethers, threo forms of arylglycerol β-syringyl ethers, erythro forms arylglycerol β-guaiacyl ethers and threo forms of arylglycerol β-guaiacyl ethers. The intensities of the cross peaks suggest larger amounts of β-syringyl ethers than β-guaiacyl ethers. The erythro isomers dominate among the β-syringyl ethers. Erythro and threo forms of β-guaiacyl ethers are present in similar amounts. © 1998 John Wiley & Sons Ltd.