Crystal and molecular structures of benzyl 3- O-benzoyl-4- O-benzyl-2- O-(2,3,6-trideoxy-α- l- glycero-hex-2-enopyranosyl-4- ulose)-α- l-rhamnopyranoside

Abstract

Benzyl 3- O-benzoyl-4- O-benzyl-2- O-(2,3,6-trideoxy-α- l- glycero-hex-2-enopyranosyl-4-ulose)-α- l-rhamnopyranoside has been investigated by X-ray diffraction methods. The crystals obtained from aqueous ethanol are orthorhombic, space group P2 12 12 1 with cell constants a = 10.775(2), b = 10.857(2), and c = 25.774(3) Å. A four-circle, automatic diffractometer was used for intensity-data collection. Out of 3370 reflection intensities, 2634 were of I > 2σ I and these were used for refinement. The structure was solved by direct methods, and the atomic parameters were then refined by the full-matrix, least-squares procedure. The unsaturated dihydropyranone ring adopts a deformed sofa conformation, whereas the rhamnopyranose ring adopts a chair conformation. The glycosidic linkage is characterised by torsion angles Φ33(2)° and Ψ-13(1)°. A new classification for the conformations of glycosidic linkages is suggested.