2-(2,4:3,5-Di-<i>O</i>-benzylidene-<scp>D</scp>-<i>glycero</i>-<scp>D</scp>-<i>allo</i>-pentitol-1-yl)pyridine, C<sub>24</sub>H<sub>23</sub>NO<sub>5</sub>
作者:A. T. H. Lenstra、H. J. Geise、E. De Vos、E. L. Esmans、F. C. Alderweireldt、J. L. M. Dillen
DOI:10.1107/s0108768192013296
日期:1993.8.1
C24H23NO5, M(r) = 405.4, orthorhombic, P2(1)2(1)2(1), a = 8.762 (1), b = 13.984 (1), c = 16.569 (1) angstrom, V = 2030 (1) angstrom3, Z = 4, D(x) = 1.327 Mg m-3, lambda(Mo Kalpha) = 0.71073 angstrom, mu = 0.087 mm-1, F(000) = 856, room temperature, wR = 0.034, R = 0.035 for 2049 observed reflections [I greater-than-or-equal-to 3sigma(I)] out of 2536 measured reflections and 341 variables. The sugar moiety has the D-allo configuration, which provides further proof that the ring closure of the title compound to an a-nucleoside follows an S(N)2-like mechanism. The title compound consists of two 1,3-dioxane rings in the chair form, trans fused to each other, with two phenyl rings and a (2-pyridyl)hydroxymethyl substituent in equatorial positions. The variation of the C-O lengths in the dioxane rings follows the rules of the anomeric effect. The 1,3-dioxane rings are more puckered than their carbon analogues in transdecalin. The pyridine ring is nearer to C(3) than to O(2), with a synclinal conformation around C(1)C(2). An intermolecular hydrogen bond is observed, but no intramolecular hydrogen bonds were found. Molecular-mechanics calculations (MM3 force field) reproduce the bond lengths with an e.s.d. of 0.011 angstrom and the valence angles with an e.s.d. of 1.0-degrees. MM3 supports conclusions drawn from the X-ray determination concerning the conformational behaviour of the free molecule. In the force field the absence of parameters dedicated to aromatic N atoms makes calculations more difficult.