Conformational features of C-glycosyl compounds: crystal structure and molecular modelling of "methyl C-gentiobioside".
The crystal of "methyl C-gentiobioside" (methyl 8,12-anhydro-6,7-dideoxy-D-glycero-D-gulo-alpha-D-gluco-trideca pyranoside) (C14H26O10) is triclinic, space group P1, with a = 1.0181 (6) nm, b = 0.8093 (5) nm, c = 0.5066 (4) nm, alpha = 96.03 (5) degrees, beta = 99.94 (5) degrees, gamma = 90.85 (5) degrees. The two D-glucose residues have the 4C1 conformation. The orientation of the beta-(1----6) linkage is characterized by torsion angles phi = 55.9 degrees, psi = 175.1 degrees, and omega = -63.9 degrees. The orientation of the primary hydroxyl group at the non-reducing residue is gauche-trans (omega' = -53.6 degrees). There is no intramolecular hydrogen bond. Molecules are held together by a network of hydrogen bonds involving all of the hydroxyl groups. This crystal structure is the first experimental characterization of a "C-disaccharide". Unlike methyl gentiobioside, which has a high level of conformational flexibility, the "C-disaccharide" has a restricted flexibility. Each of the low-energy conformers in vacuo has a value of phi centered about 60 degrees, in agreement with the solid state conformation, and the exo-anomeric effect is no longer predominant.
Neuman
A
A
Laboratoire de Chimie Structurale Biomoléculaire, U.F.R. Santé, Médecine, Université de Paris-Nord, Bobigny, France.
Longchambon
F
F
Abbes
O
O
Gillier-Pandraud
H
H
Pérez
S
S
Rouzaud
D
D
Sinaÿ
P
P
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006860:Hydrogen Bonding; D008757:Methylglucosides; D008759:Methylglycosides; D008958:Models, Molecular; D008969:Molecular Sequence Data; D013816:Thermodynamics; D014961:X-Ray Diffraction
D008757:Methylglucosides; D008759:Methylglycosides; C063987:methyl C-gentiobioside