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Crystal and molecular structures of 6-O-acetyl-2,3,4-trideoxy-α-dl-glycero-hex-2-enopyranose and 3-O-(6-O-acetyl-2,3,4-trideoxy-α-l-glycero-hex-2-enopyranosyl)-1,2;5,6-di-O-isopropylidene-α-d-glucofuranose

Carbohydrate Research
Publication Date
DOI: 10.1016/0008-6215(84)85157-5


Abstract 6- O-Acetyl-2,3,4-trideoxy-α- dl- glycero-hex-2-enopyranose ( 1) and 3- O-(6- O-acetyl-2,3,4-trideoxy-α- l- glycero-hex-2-enopyranosyl)-1,2;5,6-di- O-isopropylidene-α- d-glucofuranose ( 2) have been investigated by X-ray diffraction methods. Compound 1 crystallises in the monoclinic system, space group P2 1/a, with cell constants a = 21.123(5), b = 4.439(2), c = 10.085(2) Å, and β = 110.22(2)°. Compound 2 crystallises in the orthorhombic system, space group P2 12 12 1, with cell constants a = 22.110(6), b = 11.651(4), and c = 8.658(3) Å. 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 α- d-glucofuranose ring in 2 has a twist conformation ( T). The glycoside bond in 2 is characterized by φ and ψ torsion angles of 47(2)° and 32(2)°, respectively.

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