DISTRIBUTION OF ERYTHRO AND THREO FORMS OF DIFFERENT TYPES OF BETA-0-4 STRUCTURES IN ASPEN LIGNIN BY C-13 NMR USING THE 2D INADEQUATE EXPERIMENT

Carbon-carbon connectivity spectra of C-13-enriched aspen lignin recor ded using the 2D INADEQUATE experiment revealed cross peaks which can be assigned to four types of arylglycerol beta-aryl ethers (beta-0-4 s tructures): erythro forms of arylglycerol beta-syringyl ethers, threo forms of arylglycerol beta-syringyl ethers, erythro forms arylglycerol beta-guaiacyl ethers and three forms of arylglycerol beta-guaiacyl et hers. The intensities of the cross peaks suggest larger amounts of bet a-syringyl ethers than beta-guaiacyl ethers. The erythro isomers domin ate among the beta-syringyl ethers. Erythro and three forms of beta-gu aiacyl ethers are present in similar amounts. (C) 1998 John Wiley & So ns Ltd.