Absolute configuration from a redetermination of (+)-5-bromo-1-[(2R,4S,5R)- 4-hydr-oxy-5-(hydroxy-meth-yl)oxolan-2-yl]pyrimidine-2,4-dione at 118 (2) K

The absolute configuration of the title compound, C9H11BrN2O5, has been determined. The crystal structure is stabilized by a network of hydrogen bonds in which atoms from both the uracil and deoxy-ribose moieties of the mol-ecule participate. The stability of the structure is also affected by several short contacts that are formed by O atoms in the carbonyl groups. The original crystal structure determination [Iball, Morgan & Wilson (1966). Proc. R. Soc. London Ser. A, 295, 320-333] was carried out at room temperature and was refined from data measured by photographic methods. The present crystal structure is of significantly higher precision.