The Crystal and Molecular Structures of 5-Bromo-2'-Deoxyuridine and 5-Bromouridine

The structures of 5 -bromo-2'-deoxyuridine (BUDR) and 5-bromouridine (BUR) have been determined by X-ray single crystal analysis and the parameters (including anisotropic temperature vibrations) have been refined by the three-dimensional least squares method. For both compounds the unit cells are monoclinic and the space group is P21; the unit cell dimensions are a = 9·150 ± 0·008, b = 5·142 ± 0·004, c = 12·108 ± 0·009 Å, β = 108·2° ± 0·1° for BUDR and a = 7·725 ± 0·006, b = 5·813 ± 0·004, c = 13·264 ± 0·010 Å, β = 101·2° ± 0·1° for BUR. The value of the agreement index for 1221 independent reflexions for BUDR was 0·074, and for 1312 independent reflexions for BUR it was 0·070. The standard deviations of atomic positions are about 0·02 Å. Comparison with other nucleosides and nucleotides shows that the glycosidic bond length in BUDR is shorter than normal and that the conformation of the C5'— O5' bond is not that most commonly found. In BUR, the glycosidic bond length and the C5'— O5' bond conformation are normal.