Structure of 1,2-O-(2,2,2-trichloroethylidene)-α-D-glucofuranose (α-D-chloralose)

Abstract

CsHI1C1306, M r = 309.47, hexagonal , P32, a = 13.383 (3), c = 5.692 (2) A, V = 883.0 A 3, Z = 3, Dx = 1.746, D,, = 1.755 Mg m -a, ~(Mo Ka) = 0.71073 A, p ( M o Ka) = 0 .792 m m k The structure was solved by direct methods and refined to R(F) = 0.050 for 992 independent reflexions. The glucofuranose and dioxolane rings have aT 4 and °I2~E conformat ions , respectively, and these two rings are rigidly fused. The molecules are packed in a left-handed helix ar rangement along the c axis. The furanose-ring O atoms form intermolecular hydrogen bonds with the 0 ( 3 ) hydroxyl groups. The intermolecular hydrogen bonds between the 0 ( 5 ) and 0 ( 6 ) hydroxyl groups form right-handed double-helix chains around a threefold screw axis. C I . . . C I intermolecular contacts (3.45 A) were observed about another threefold screw axis. Introduction. a-D-Chloralose crystallized from an e thano l -wa te r solution at room temperature. A crystal with dimensions 0 .17 x 0 .20 x 0.33 mm was used to collect 1967 intensities of the hkl and h/~i reflexions by 09-20 scans to 0 = 50 ° on a Rigaku AFC-5 diffractometer. The structure was solved with M U L T A N (Main, Woolfson, Lessinger, Germain & Declercq, 1977), using 150 reflexions for phase generation. The first E map revealed all of the non-H atoms. The chemically known absolute structure was correctly given for space group P32 (two possible space groups, P31 and P3z, were indicated from the systematic absences 00l with l =~ 3n). The structure was refined by full-matrix least squares, minimizing } wlF o kFcI 2 with w l = t72(Fo) + (0.023Fo) 2 and where a(Fo) is the s tandard deviation of Fo from counting statistics. All H atoms were located from difference Fourier maps and refined isotropically. The final values of R = }'[F o klFcl[/~'lFol and g w = ( ~ w [ F o k l f c I [z/}'. ifolZ)l/Z were 0 .050 and 0.062, respectively, for 992 independent reflexions [F o > 3a(Fo)]. The atomic scattering factors for all a toms were obtained from International Tables for X-ray Crystallography (1974). All computa t ions were performed on a F A C O M M200 computer at the Data Processing Center, Kyo to University, using the KPAX program system. The atomic parameters are given in Tables 1 and 2.* * Lists of structure factors and anisotropic thermal parameters have been deposited with the British Library Lending Division as Supplementary Publication No. SUP 36731 (7 pp.). Copies may be obtained through The Executive Secretary, International Union of Crystallography, 5 Abbey Square, Chester CH 1 2HU, England. Table 1. Atomic coordinates for non-hydrogen atoms in a-D-chloralose Estimated standard deviations are given in parentheses. B~, is the isotropic equivalent of the anisotropic thermal parameters (Hamilton, 1959).