title: Crystal and molecular structures of 6-O-acetyl-2,3,4-trideoxy-alpha-DL-glycero-hex-2-enopyranose and 3-O-(6-O-acetyl-2,3,4-trideoxy-alpha-L-glycero-hex-2-enopyranosyl++ +)-1,2 ;5,6-di-O-isopropylidene-alpha-D-glucofuranose.
abstract: 6-O-acetyl-2,3,4-trideoxy-alpha-DL-glycero-hex-2-enopyranose (1) and 3-O-(6-O-acetyl-2,3,4-trideoxy-alpha-L-glycero-hex-2-enopyranosyl) -1,2;5,6-di-O-isopropylidene-alpha-D-glucofuranose (2) have been investigated by X-ray diffraction methods. Compound 1 crystallises in the monoclinic system, space group P21/a, with cell constants a = 21.123(5), b = 4.439(2), c = 10.085(2) A, and beta = 110.22(2) degrees. Compound 2 crystallises in the orthorhombic system, space group P212121, with cell constants a = 22.110(6), b = 11.651(4), and c = 8.658(3) A. The intensity data were collected in a four-circle automatic diffractometer, with 1488 reflections for 1, and 2151 for 2. The structures were solved by direct methods. The atomic parameters were refined in an anisotropic mode by the full-matrix, least-squares procedure against 1065 and 1884 observed reflections for 1 and 2, respectively, giving R = 0.046 for each compound. The 2-enopyranose rings in 1 and 2 adopt half-chair conformations (H), and that in 2 is markedly deformed. The 1,2-dioxolane ring in 2 has an envelope (E) conformation, whereas the 5,6-dioxolane ring is dynamically disordered and can be represented by a conformational hybrid (E + P). The alpha-D-glucofuranose ring in 2 has a twist conformation (T). The glycoside bond in 2 is characterized by phi and psi torsion angles of 47(2) degrees and 32(2) degrees, respectively.
mesh_terms: D003461:Crystallography; D004187:Disaccharides; D006601:Hexoses; D008968:Molecular Conformation; D014961:X-Ray Diffraction
chemical_list: D004187:Disaccharides; D006601:Hexoses