A refinement of the crystal structure of cytidine

Abstract

The crystal structure of cytidine has been refined by least-squares calculations to a final R index of 5.6 %. Three-dimensional photographic data were used. The essential features of the original structure are confirmed, but the standard deviations in the bond lengths are reduced to about 0.006 A and in the bond angles to less than 0.5 . The distances and angles in the cytosine part of the molecule are closely similar to those found in cytosine monohydrate. The two angles at each external bond to pyrimidine appear to differ significantly. The N-glycosidic linkage is found to be 1.497 A. The two bonds to the furanose ring oxygen atom differ in length by 0.03 A. The existence of an intramolecular C-H O interaction at 3.23 /k is confirmed. A REFINEMENT OF THE CRYSTAL STRUCTURE OF CYTIDINE T&ble 1. Observed and calculated structure factors Within the groups of constant k the columns contain h, l, lOIFol, IOIFe[ and the phase angle in degrees.