Lignin–carbohydrate model compounds. Formation of lignin–methyl arabinoside and lignin–methyl galactoside benzyl ethers via quinone methide intermediates

Model compounds for lignin–carbohydrate complexes (LCCs) were synthesized from β-O-4-type quinone methides and methyl glycosides of α-L-arabinofuranose and α-D-galactopyranose. Both monosaccharides reacted predominantly through primary hydroxy groups with the benzyl position of the dilignol but some secondary C-3 hydroxy groups of galactopyranosides also took part in ether-bond formation. Methyl α-L-arabinofuranosides were found to be more reactive than methyl α-D-galactopyranosides. LCC model-compound formation via quinone methides gave a mixture of four diastereomers. The diastereomers were isolated using silica gel and HPLC chromatography and all products were characterized by NMR spectroscopy.