organic compounds
The title compound, 2,4-diamino-5-bromo-7-(2-deoxy-2-fluoro--D-arabinofuranosyl)-7H-pyrrolo[2,3-d]pyrimidine, C11H13BrFN5O3, shows two conformations of the exocyclic C4'-C5' bond, with the torsion angle (O5'-C5'-C4'-C3') being 170.1 (3)° for conformer 1 (occupancy 0.69) and 60.7 (7)° for conformer 2 (occupancy 0.31). The N-glycosylic bond exhibits an anti conformation, with = -114.8 (4)°. The sugar pucker is N-type (C3'-endo; 3T4), with P = 23.3 (4)° and m = 36.5 (2)°. The compound forms a three-dimensional network that is stabilized by several intermolecular hydrogen bonds (N-HO, O-HN and N-HBr).