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 P 1 (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 1 C 4 and 4 C 1 conformations, respectively. The interresidue torsion angles are comparable with those generated in a recent molecular modelling study.