STRUCTURE OF 1-(2-DEOXY-BETA-D-RIBOPYRANOSYL)-5-IODOURACIL

1-(2-Deoxy-beta-D-ribopyranosyl)-5-iodouracil, C9H11IN2O5, M(r) = 354.10, monoclinic, P2(1), a = 5.458 (3), b = 8.237 (4), c = 12.812 (6) angstrom, beta = 98.42 (4)-degrees, V = 569.8 (5) angstrom3, Z = 2, D(m) = 2.05, D(x) = 2.063 Mg m-3, lambda-(Mo K-alpha) = 0.71069 angstrom, mu = 2.789 mm-1, F(000) = 344, T = 293 K, final R = 0.039 for 1701 unique observed [F greater-than-or-equal-to 4-sigma(F)] reflections. The sugar ring adopts a slightly flattened chair conformation. The heterocyclic base is placed in an - ap (antiperiplanar) orientation [chi = 196.4 (3)-degrees] with respect to the sugar moiety. Of the three sugar ring substituents, only O(33') is in an axial position. The packing of the crystal is determined by three intermolecular hydrogen bonds, involving O(33'), O(2) and O(44'). The conformational parameters are in accordance with the IUPAC-IUB Joint Commission on Biochemical Nomenclature [Pure Appl. Chem. (1983), 55, 1273-1280] guidelines.