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′-De­oxy-2-fluoro­tubercidin

In the title compound [systematic name: 7-(2-de­oxy-β-D-erythro-pentofuranos­yl)-2-fluoro-7H-pyrrolo[2,3-d]pyrimidin-2-amine], C₁₁H₁₃FN₄O₃, the conformation of the N-glycosylic bond is between anti and high-anti [χ = −110.2 (3)°]. The 2′-deoxy­ribofuranosyl unit adopts the N-type sugar pucker (₄T³), with P = 40.3° and τ_m = 39.2°. The orientation of the exocyclic C4′—C5′ bond is −ap (trans), with a torsion angle γ = −168.39 (18)°. The nucleobases are arranged head-to-head. The crystal structure is stabilized by four inter­molecular hydrogen bonds of types N—H...N, N—H...O and O—H...O.

6-Aza-2′-deoxy­uridine and N³-anisoyl-6-aza-2′-deoxy­uridine

In 2-(2-deoxy-β-D-erythro-pentofuranosyl)-1,2,4-triazine-3,5(2H,4H)-dione (6-aza-2′-deoxy­uridine), C₈H₁₁N₃O₅, (I), the conformation of the glycosylic bond is between anti and high-anti [χ = −94.0 (3)°], whereas the derivative 2-(2-deoxy-β-D-erythro-pentofuranosyl)-N⁴-(2-methoxy­benzoyl)-1,2,4-triazine-3,5(2H,4H)-dione (N³-anisoyl-6-aza-2′-deoxy­uridine), C₁₆H₁₇N₃O₇, (II), displays a high-anti conformation [χ = −86.4 (3)°]. The furanosyl moiety in (I) adopts the S-type sugar pucker (²T₃), with P = 188.1 (2)° and τ_m = 40.3 (2)°, while the sugar pucker in (II) is N (³T₄), with P = 36.1 (3)° and τ_m = 33.5 (2)°. The crystal structures of (I) and (II) are stabilized by inter­molecular N—H...O and O—H...O inter­actions.

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.

The 7-bromo derivative of 2-amino-2'-deoxy­tubercidin fluorinated at the sugar moiety

The title compound, 2,4-diamino-5-bromo-7-(2-deoxy-2-fluoro-[beta]-D-ara­bino­furanosyl)-7H-pyrrolo[2,3-d]pyrimidine, C₁₁H₁₃BrFN₅O₃, shows two conformations of the exocyclic C4'-C5' bond, with the torsion angle [gamma] (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 [chi] = -114.8 (4)°. The sugar pucker is N-type (C3'-endo; ³T₄), with P = 23.3 (4)° and [tau]_m = 36.5 (2)°. The compound forms a three-dimensional network that is stabilized by several inter­molecular hydrogen bonds (N-H...O, O-H...N and N-H...Br).