Lignin-carbohydrate model compounds. Reactivity of methyl 3-O-(#alpha#-L-arabinofuranosyl)-#beta#-D-xylopyranoside and methyl #beta#-D-xylopyranoside towards a #beta#-O-4-quinone methide

摘要

The reactivity of a disaccharide, namely methyl 3-O-(#alpha#-L-arabinofuranosyl)-#beta#-D-xylopyranoside, and that of a monosaccharide, methyl #beta#-D-xylopyranoside towards a lignin #beta#-O-4 quinone methide were compared as a model reaction for the formation of lignin-carbohydrate complexes (LCCs). Benzyl ethers were formed via a #beta#-O-4 quinone methide giving 4 diastereomers of each product. All three secondary hydroxy groups of methyl #beta#-D-xylopyranoside but only the primary hydroxy group of the arabinofuranosyl moiety of methyl 3-O-(#alpha#-L-arabinofuranosyl)-#beta#-D-xylopyranoside became etherified to the benzyl position of the lignin #beta#-aryl ether model compound. The LCC model compounds were isolated as individual diastereomers or mixtures of diastereomers using silica gel and HPLC chromatography and they were all characterized by NMR spectroscopy and MS.