Crystal and molecular structure of methyl O-α-d-mannopyranosyl-(1→2)-α-d-mannopyranoside

The crystal and molecular structure of a synthetic mannosyl disaccharide, methyl O-α-d-mannopyranosyl-(1→2)-α-d-mannopyranoside, has been determined from X-ray diffractometer data by direct methods by use of the MULTAN programs. The crystals are monoclinic, space group P2₁ with unit cell dimensions, a 8.086(1), b 9.775(1), c 9.975(2) Å, β 104.58(1)°, Z 2, and D_m 1.54 g/cm³. The structure was refined to an R-value of 0.033 for 1359 reflections measured with CuKα radiation. The mannopyranose units have the chair conformations ⁴C₁(d) with C-5′ and C-2′ deviating from the best plane through the other four atoms of the ring by -0.68 and +0.53 Å in the nonreducing group, and C-3 and O-5 deviating from the mean plane through the other four atoms by +0.57 and -0.66 Å, respectively, in the "potentially" reducing residue. The ring-to-ring conformation can be described as (φ,ψ) = (-64.5, 105.5°). The conformation across the C-5-C-6 bond is gauche-gauche in both the sugars. The crystal structure is stabilized by a network of intermolecular O-H {A figure is presented} O hydrogen bonds.