1,7-Dideaza-2′-deoxy-6-nitronebularine: a pyrrolo[2,3-b]pyridine nucleoside with an intramolecular hydrogen bond stabilizing thesynconformation

Abstract

The title compound [systematic name: 1-(2-deoxy-β-D-erythro-pentofuranosyl)-4-nitro-1H-pyrrolo[2,3-b]pyridine], C12H13N3O5, forms an intramolecular hydrogen bond between the pyridine N atom as acceptor and the 5′-hydroxy group of the sugar residue as donor. Consequently, the N-glycosylic bond exhibits asynconformation, with a χ torsion angle of 61.6 (2)°, and the pentofuranosyl residue adopts a C2′-endoenvelope conformation (2E,S-type), withP= 162.1 (1)° and τm= 36.2 (1)°. The orientation of the exocyclic C4′—C5′ bond is +sc(gauche,gauche), with a torsion angle γ = 49.1 (2)°. The title nucleoside forms an ordered and stacked three-dimensional network. The pyrrole ring of one layer faces the pyridine ring of an adjacent layer. Additionally, intermolecular O—H...O and C—H...O hydrogen bonds stabilize the crystal structure.