Synthesis, crystal structure, and conformation of 3- O-(6- O-acetyl-2,3-anhydro-4-deoxy-α- l- ribo-hexopyranosyl)-1,2:5,6-di- O-isopropylidene-α- d-glucofuranose

Abstract

3- O-(6- O-Acetyl-2,3-anhydro-4-deoxy-α- l- ribo-hexopyranosyl)-1,2:5,6-di- O-isopropylidene-α- d-glucofuranose has been synthesised and its monocrystal investigated by X-ray diffraction methods. The compound crystallises in the orthorhombic system, space group P2 12 12 1, with cell constants a = 8.790(7), b = 11.678(4), and c = 21.457(10) Å. The intensity data were collected with a four-circle CAD-4 diffractometer. From a total of 1684 intensities, 1275 were of I > 2σ I. The structure was solved by direct methods and refined by the full-matrix, least-squares procedure, resulting in R 0.057. The 4-deoxy-2,3-anhydropyranose ring is characterised by a sofa conformation ( 5 E), the 1,2- O-isopropylidene ring has a hybrid conformation ( E + T), and the 5,6- O-isopropylidene and the α- d-glucofuranose rings have twist ( T) conformations. The φ and ψ torsion angles for the glycosidic linkage are 54(4)° and 29(4)°, respectively.