Synthesis of methyl 3,4-di-O-(β-D-xylopyranosyl)-β-D-xylopyranoside, a methyl β-xylotrioside related to branched xylans

The condensation of 2,3,4-tri-O-acetyl-α-D-xylopyranosyl bromide (I) with methyl 2-O-benzyl-β-D-xylopyranoside (II) afforded methyl 2-O-benzyl-3,4-di-O-(2,3,4-tri-O-acetyl-β-D-xylopyranosyl)-β-D-xylopyranoside (III). Hydrogenolytic cleavage of the benzyl group from III and subsequent deacetylation led to the crystalline title methyl β-xylotrioside (V) related to branched xylans. Compound V was characterized by its crystalline per-O-acetate VI and per-O-methyl derivative VII.