Crystals of uridine, C9HI2N206, are monoclinic, space group P21 with a=4.981 (4), b= 14.649 (8), c= 13"964 (8)A, fl= 95"45 (8) ° and Z= 4, The structure was solved by the direct method and refined by least-squares calculations, using Ni-filtered Cu Ke diffractometer data. The final R index was 0.033 for 2232 reflections, and the standard deviations in the atomic positions are about 0.003 A. The two independent molecules have very similar conformations; the conformation about the glycosidic bond is anti, the sugar ring is puckered with C(Y) endo, and the conformation about C(4")-C(5') is gauchegauche.

No abstract

No abstract

No abstract

The crystal structure of 1,2:4,5-di-O-isopropylidene-p-D-fructopyranose, C12H2006, has been determined.The crystals are monoclinic, P21, with a= 11.094(7), b=5.626(4), c= 11.917(7) A, fl=115.53(8) ° and Z= 2. The structure was refined by the full-matrix least-squares technique to an R value of 0.047, using 1281 independent three-dimensional single-crystal X-ray data collected with an automatic four-circle diffractometer. The fl-anomer configuration previously assumed without proof was confirmed. Each 1,3dioxolane ring has an envelope conformation (E) and the six-membered ring is a chair (2Cs) somewhat distorted towards a half-chair (2Ho). The molecules are arranged in a polar helix joined together by hydrogen bonds around the screwaxis and they fit together well bytilting in the direction of the pitch of the screw.