The conformation of tetrafluorinated methyl galactoside anomers: crystallographic and NMR studies. - Archive ouverte HAL
Article Dans Une Revue Carbohydrate Research Année : 2011

The conformation of tetrafluorinated methyl galactoside anomers: crystallographic and NMR studies.

Résumé

The first single-crystal X-ray diffraction study of tetrafluorinated monosaccharide derivatives is presented. Both α- and β-methyl 2,3-dideoxy-2,2,3,3-tetrafluoro-d-galactopyranoside anomers adopt the (4)C(1) conformation. The values for the C1-O1 and C1-O5 bond lengths and the O5-C1-O1-CH(3) dihedral angles are in line with what can be expected from the anomeric and exo-anomeric effects. The chair conformations are slightly distorted, presumably due to repulsion between 1,3-diaxial C-O and C-F bonds. The asymmetric unit of both compounds contains up to three independent molecules, which differ in the conformation of the hydroxymethyl group (including in one case a 'forbidden'gg rotamer). The molecular packing of the β-anomer shows a clear segregation between fluorinated and hydrophilic domains, while for the α-anomer the regions of fluorine segregation are broken by interleafing of OMe groups. There is one close OH⋯F contact, which is likely to arise from the crystal packing. NMR studies show that the two anomers also adopt a (4)C(1) conformation in solution (D(2)O, CDCl(3)).

Domaines

Chimie organique

Dates et versions

hal-00991612 , version 1 (15-05-2014)

Identifiants

Citer

Bruno Linclau, Samuel Golten, Mark Light, Muriel Sebban, Hassan Oulyadi. The conformation of tetrafluorinated methyl galactoside anomers: crystallographic and NMR studies.. Carbohydrate Research, 2011, 346 (9), pp.1129-1139. ⟨10.1016/j.carres.2011.04.007⟩. ⟨hal-00991612⟩
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