2′-De­oxy-5-propynyl­cytidine: a nucleoside forming two solid-state conformations

The title compound, 4-amino-1-(2-deoxy-β-D-erythropentofuranosyl)-5-(prop-1-ynyl)pyrimidin-2(1H)-one, C₁₂H₁₅N₃O₄, shows two conformations in the crystalline state which differ mainly in the glycosylic bond torsion angle and the sugar pucker. Both mol­ecules exhibit an anti glycosylic bond conformation, with torsion angles χ = −135.0 (2) and −156.4 (2)° for mol­ecules 1 and 2, respectively. The sugar moieties show a twisted C2′-endo sugar pucker (S-type), with P = 173.3 and 192.5° for mol­ecules 1 and 2, respectively. The crystal structure is characterized by a three-dimensional network that is stabilized by several inter­molecular hydrogen bonds between the two conformers.

2′-Deoxy­immunosine: a thia­zolo[4,5-d]pyrimidine nucleoside adopting the syn conformation

The title compound [systematic name: 5-amino-3-(2-deoxy-β-D-erythro-pento­furanosyl)thia­zolo[4,5-d]pyrimidine-2,7-(3H,6H)-dione], C₁₀H₁₂N₄O₅S, exhibits a syn glycosylic bond conformation, with a torsion angle χ of 61.0 (3)°. The furan­ose moiety adopts the N-type sugar pucker (³T₄), with P = 33.0 (5)° and τ_m = 15.1 (1)°. The conformation at the exocyclic C4′—C5′ bond is +ap (trans), with the torsion angle γ = 176.71 (14)°. The extended structure is a three-dimensional hydrogen-bond network involving O—H...O and N—H...O hydrogen bonds.