Crystal structure of methyl α-D-galactopyranoside monohydrate

Abstract

Methyl e-D-galactopyranoside monohydrate crystallizes in the orthorhombic space group P2x2121 with cell dimensions a= 6.130, b=7.486, c=21.202 A. The structure was solved using the tangent formula and refined by full-matrix least-squares to a final reliability index of 0.032. Bond lengths and angles are normal with the primary hydroxyl group in the gauche-trans arrangement; the ring conformation is the expected chair form (C1). The ring oxygen atom participates in the hydrogen bonding scheme which also contains a bifurcated hydrogen bond. The environment of the water molecule comprises a planar array of oxygen atoms which approximate a square.

The crystal and molecular structure of an aldotriouronic acid trihydrate: O-(4-O-methyl-α-D-glucopyranosyluronic acid)-(1-2)-O-β-D-xylopyranosyl-(1-4)-D-xylopyranose trihydrate

“…0(2') and O(3'), in contrast, participate in one (as donor) and three (one as donor and two as acceptor) hydrogen bonds, respectively. The rather unusual behavior of 0(3') in that it accepts two hydrogen bonds has also been observed in the structures of e-lactose monohydrate (Fries, Rao & Sundaralingam, 1971) and methyl e-galactoside monohydrate (Gatehouse & Poppleton, 1971a).…”

“…An increase in flexibility between rings due to the absence of the hydrogen bond apparently permits the reducing xylose unit to seek a conformation that diminishes the bridge oxygen angle. The values of 113.0, 113.5, and 113.2 ° for the glycosidic oxygen angles in methyl ~-D-glucoside (Berman & Kim, 1968), methyl ~-D-galactoside (Gatehouse & Poppleton, 1971a), and methyl ~-D-altropyranoside (Gatehouse & Poppleton, 1971b) are about 3 to 4 ° smaller than the bridge oxygen angles of 117.6 and 117.2 ° for methyl fl-D-maltoside (Chu & Jeffrey, 1967) and maltose (Quigley, Sarko & Marchessault, 1970). Both of these disaccharide structures contain an intramolecular hydrogen bond.…”

Precision X-ray and neutron diffraction studies of methyl β-D-ribopyranoside, C6H12O5

“…The methoxyl group is oriented such that C(6) is antiperiplanar to C(2). This type of arrangement has been found for a large number of methyl glycosides in which O(1) is axially oriented on a six-membered ring: methyl ~t-D-glucopyranoside (Berman & Kim, 1968), methyl st-D-mannopyranoside (Gatehouse & Poppleton, 1970), methyl ~-D-galactopyranoside monohydrate (Gatehouse & Poppleton, 1971a), methyl st-D-altropyranoside (Gatehouse & Poppleton,197 l b), methyl 5-thio-,-D-ribopyranoside (Girling & Jeffrey, 1973a), methyl ~t-D-xylopyranoside triacetate (James & Stevens, 1974), and methyl fl-o-arabinopyranoside (McConnell, Schwartz & Stevens, 1977). Molecularorbital calculations (Jeffrey, Pople & Radom, 1974) have shown that this arrangement corresponds to the minimum energy for the orientation of the methoxyl group.…”

The crystal structure of 4-O-β-D-galactopyranosyl-L-rhamnitol

“…The galactopyranose ring is the normal 4C 1 chair (Stoddart, 1971), but the ring distortion is greater than in the n and fl galactose structures (Longchambon, Ohannessian& Neuman, 1975;Sheldrick, 1976) and in methyl n-D-galactose hydrate (Gatehouse & Poppleton, 1971), where the ring torsion angles lie in the more commonly observed range of 54 to 64 ° . This distortion is also shown by the relatively large values for the q2 and 8 puckering parameters (Cremer & Pople, 1975 sumably because of the intramolecular hydrogen bond from the hydroxyl to the galactose ring oxygen.…”