(2-O-α-d-Galactopyranosyl-4-O-methyl-α-d-glucurono)-d-xylan from Eucalyptus globulus Labill

An unusual heteroxylan composed of galactosyl, 4-O-methyl-glucuronosyl and xylosyl residues with molar ratio 1:3:30 was isolated from the wood of Eucalyptus globulus Labill. The results of linkage analysis, supported by data of 1H, 2D 1H–1H COSY and 13C NMR spectroscopy, revealed that the polysaccharide is a (2-O-α-d-galactopyranosyl-4-O-methyl-α-d-glucurono)-d-xylan with a (1→4)-linked β-d-xylopyranosyl backbone branched at O-2 by short side chains composed of terminal 4-O-methyl-α-d-glucuronic acid and of 4-O-methyl-α-d-glucuronic acid substituted at O-2 with α-d-galactose.