Evidence for an ester linkage between lignin and glucuronic acid in lignin-carbohydrate complexes by DDQ-oxidation.

Ester linkages between the carboxyl group in glucuronic acid and lignin in lignified plant cell walls have often been demonstrated by alkaline degradation or sodium borohydride reduction of acidic lignin-carbohydrate complexes (LCC).1~3)However, each of these methods has one serious disadvantage that the binding unit toward the glucuronic acid residue is indeterminate.In this article, we report a novel technique to obtain direct evidence for ester linkages between glucuronic acid and lignin by adopting selective cleavage of methoxybenzyl glucuronate with 2,3dichloro-5,6-dicyano-l ,4-benzoquinone (DDQ).Previously, we analyzed the ether type of lignin-