The Crystal and Molecular Structure of 3-Chloro-3-deoxy-1,2;5,6-di-O-isopropylidene-β-D-idose

Abstract

The crystal and molecular structure of 3-chloro-3-deoxy-1,2;5,6-di-O-isopropylidene--~-idose has been determined from three dimensional X-ray data collected by counter methods. The structure was refined by fullmatrix least-squares techniques to a conventional R factor of 5.7% for the 817 observed reflections. The compound crystallizes in the orthorhombic space group P2,2,2, with four molecules in a cell of dimensions a = 9.744(6), b = 26.76(2), c = 5.403(3) A.The structure analysis has served to confirm the site of halogenation and that it occurs stereospecifically. The conformation of the furan ring is an envelope arrangement with C(4) displaced from the mean plane.La structure cristalline et moltculaire du 3-chloro-3-d~oxy-l,2;5,6-di-O-isopropylid6ne--~-idose a ete dbterminee a partir des donnCes tridimensionnelles de rayons-X obtenues par des mtthodes de comptage. La structure a ete affinbe par moindres carres (matrice complbte) jusqu'a un facteur d'accord R = 5.7% pour 817 reflexions observ6es. Le compose cristallise dans le syst6me orthorhombique groupe d'espace P2,2,2,, avec quatre molbcules dans une maille de dimensions a = 9.744(6), b = 26.76(2), c = 5.403(3) A.La determination de la structure a semi a confirmer le site de l'halogknation ainsi que le fait de sa stereosptcificitb. La conformation du noyau du furanne est un arrangement en enveloppe avec le C, dkplact par rapport au plan central.Canadian Journal of Chemislry, 50, 93(1972) Introduction It has been found that some procedures (1, 2) for halogenation of sugars have resulted in the rearrangement of the acetal linkage. In order to both establish unequivocally the position of chlorination in the triphenylphosphine/carbon tetrachloride (TPP/CCl,) reaction (3) with 1,2; 5,6-di-0-isopropylidene-p-D-talose (I), and also to examine the detailed conformation of the molecule we have determined the crystal structure of the title compound (2). ExperimentalCompound 2 was prepared by reacting 1,2;5,6-di-0-isopropylidene-8-D-talose with TPP/CCI, (3). Colorless needle-shaped single crystals suitable for diffraction studies were obtained by recrystallization from petroleum ether (b.p. 30-60"). Weissenberg photographs of the nets hk0-hk2 inclusive using CrKa radiation together with precession photographs of the zones hOl, and Oklusing MoKa radiation, showed systematic absences for hOO: h = 2 n + 1, OkO: k = 2n + 1, 001: 1 = 2n + I. This combined with the Laue group mmm, indicated unambiguously the space group P2,2,2,.Crystal Data CI~HI,CIO, f.w. = 278.7 Orthorhombic, a = 9.744(6), b = 26.76(2), c = 5.403(3) A, V = 1408.8 A3, PO 1.27 g ~m -~, Z = 4, pc 1.31 g~m -~, 22 "C, p(MoKa) = 2.9 cm-', I M o K a = 0.7107 A.Two crystals were used to provide the diffraction data; the crystal used for intensity measurements had dimensions 0.14 x 0.1 1 x 0.51 mm. The direction of greater elongation (c axis) was parallel to @. Cell constants were determined using MoKB radiation I = 0.63225 A by applying a leastsquares fit to 12 high angle reflections (the numbers in parenthes...

Conformational Studies on the 1,2;5,6-Di-O-isopropylidene-D-hexoses

“…The "tails" of the compounds investigated were twisted in the same manner and to the same extent (--24O). The sense and extent of this twist have been confirmed by two crystal structures (15,10). The H,-H, coupling parameters also indicate that the "tails" of these compounds have definite preferred rotamers.…”

“…trans arrangement (10,17) show C-4 to be the atom displaced. This work indicates an HI-H, dihedral angle less than 10 to 12", a result also in accord with X-ray analysis of related molecules.…”

“…These perturbations would then have their major effect on the size of the Karplus constants. Using this approach, a consistent and complete solution of the conformations of the four furan rings (1,4,7,10) has been obtained (see Fig. 1 ).…”