Constrained nucleoside analogues – crystal and molecular structure of 6,5’ - O-anhydrouridines fixed in the anti conformation.

Abstract

A series of analogues of anhydrouridine have been synthesized and their crystal structures established using X-ray diffraction. For all cases, the ribose ring has O(4')-exo, C(4')-endo pucker and the pyrimidine base is in the anti conformation. Investigated compounds crystallise in different crystal systems (monoclinic, orthorhombic), have different space group symmetry (P21, P212121) and exhibit different intermolecular interactions (halogen and hydrogen bonds) among molecules in their crystal lattices. Moreover, in the case of the 5-benzyl-6,5'-O-anhydrouridine a significant positional disorder is present with the phenyl rings existing in two orientations.