Oligosaccharides related to xyloglucan: Synthesis and X-ray crystal structure of methyl 2-O-(α-l-fucopyranosyl)-β-d-galactopyranoside

The disaccharides methyl 2-O-(α-l-fucopyranosyl)-β-d-galactopyranoside and methyl 2-O-(α-l-fucopyranosyl)-α-d-galactopyranoside have been synthesised using the assisted halide reaction of tri-O-benzyl-α-l-fucopyranosyl bromide with methyl 3,4,6-tri-O-benzyl-β-d-galactopyranoside and methyl 3,4,6-tri-O-benzyl-α-d-galactopyranoside to construct the interresidue glycosidic linkages. A crystal structure of methyl 2-O-(α-l-fucopyranosyl)-β-d-galactopyranoside was determined using Mo-Kα X-ray data at 183 K. The space group is P1 (No. 1) with the unit cell containing two molecules of the disaccharide with unique conformations and a water molecule. The structure was refined to R = 0.0566 for 2969 reflections. The l-fucopyranosyl and d-galactopyranosyl residues have the nominal 1C4 and 4C1 conformations, respectively. The interresidue torsion angles are comparable with those generated in a recent molecular modelling study.