STRUCTURE OF 1-(3-DEOXY-3-PHENYLSELENO-2,5-DI-O-PIVALOYL-BETA-D-XYLOFURANOSYL)URACIL

C25H23N2O7Se, M(r) = 542.43, monoclinic, C2, a = 21.078 (1), b = 7.036 (2), c = 19.603 (1) angstrom, beta = 109.05 (1)-degrees, V = 2748.1 (7) angstrom 3, Z = 4, D(x) = 1.311 Mg m-3, lambda(Cu K-alpha(1)) = 1.54050 angstrom, mu = 2.238 mm-1, F(000) = 1108, T = 295 K, final R = 0.037 for 2191 reflections. The sugar conformation and puckering parameters are 2E with P = -15.8-degrees and psi(m) = 40.3-degrees. The N-glycosidic torsion angle chi has a value of 142.6 (4)-degrees in the anti range. The C4'-C5' side-chain conformation is -ap with gamma = -175.7 (6)-degrees. The conformation parameters are in accordance with the IUPAC-IUB Joint Commission on Biochemical Nomenclature [Pure Appl. Chem. (1983). 55, 1273-1280] guidelines.