7‐Vinyl‐8‐aza‐7‐de­aza‐2′‐deoxy­adenosine monohydrate

In the title compound, 4‐amino‐1‐(2‐deoxy‐β‐d ‐eythro‐pento­furan­osyl)‐3‐vinyl‐1H‐pyrazolo­[3,4‐d]­pyrimidine monohydrate, C₁₂H₁₅N₅O₃·H₂O, the conformation of the gly­cosyl bond is anti. The furan­ose moiety is in an S conformation with an unsymmetrical twist, and the conformation at the exocyclic C—C(OH) bond is +sc (gauche, gauche). The vinyl side chain is bent out of the heterocyclic ring plane by 147.5 (5)°. The three‐dimensional packing is stabilized by O—H·O, O—H·N and N—H·O hydrogen bonds.     

The regioisomeric 1H(2H)‐pyrazolo[3,4‐d]pyrimidine N1‐ and N2‐(2′‐deoxy‐β‐D‐ribofuranosides)

In the title regioisomeric nucleosides, alternatively called 1‐(2‐deoxy‐β‐d ‐erythro‐furan­osyl)‐1H‐pyrazolo­[3,4‐d]­pyrimidine, C₁₀H₁₂N₄O₃, (II), and 2‐(2‐deoxy‐β‐d ‐erythro‐furan­osyl)‐2H‐pyrazolo­[3,4‐d]pyrimidine, C₁₀H₁₂N₄O₃, (III), the conformations of the gly­cosyl­ic bonds are anti [?100.4 (2)° for (II) and 15.0 (2)° for (III)]. Both nucleosides adopt an S‐type sugar pucker, which is C2′‐endo‐C3′‐exo (²T₃) for (II) and 3′‐exo (between ₃E and ⁴T₃) for (III).     

The high‐anti conformation of 8‐aza‐1,3‐dide­aza‐2′‐deoxy­adenosine

In the title compound, 4‐amino‐1‐(2‐deoxy‐β‐d ‐erythro‐pento­furan­osyl)‐1H‐benzotriazole, C₁₁H₁₄N₄O₃, the conformation of the N‐glycosidic bond is in the high‐anti range [χ = ?77.1 (4)°] and the 2′‐deoxy­ribo­furan­ose moiety adopts a 2′‐­endo (²E) sugar puckering. The 5′‐hydroxyl group is disordered and has conformations ap with γ = 171.1 (3)° [occupation of 61.4 (3)%] and +sc with γ = 52.4 (6)° [occupation of 38.6 (3)%]. The nucleobases are stacked in the crystal state.     

The α‐d anomer of 5‐aza‐7‐deaza‐2′‐deoxyguanosine

In the monohydrate of 2‐amino‐8‐(2‐deoxy‐α‐d ‐erythro‐pento­furan­osyl)‐8H‐imidazo­[1,2‐a]­[1,3,5]­triazin‐4‐one, C₁₀H₁₃N₅O₄·H₂O, denoted (I) or αZ_d, the conformation of the N‐gly­cosyl­ic bond is in the high‐anti range [χ = 87.5 (3)°]. The 2′‐deoxy­ribo­furan­ose moiety adopts a C2′‐endo,C3′‐exo(^2′T_3′) sugar puckering (S‐type sugar) and the conformation at the C4′—C5′ bond is ?sc (trans).     

2′‐Deoxy‐5‐methylisocytidine

In the title compound, 2‐amino‐1‐(2‐deoxy‐β‐d ‐erythro‐pento­furan­osyl)‐5‐methyl­pyrimidin‐4(1H)‐one, C₁₀H₁₅N₃O₄, the conformation of the N‐glycosidic bond is syn and the 2‐deoxy­ribo­furan­ose moiety adopts an unusual ^OT₁ sugar pucker. The orientation of the exocyclic C4′—C5′ bond is +sc (+gauche).     

5‐Methyl‐6‐aza‐2′‐deoxy­isocytidine

In the title compound, 3‐amino‐2‐(2‐deoxy‐β‐d ‐erythro‐pento­furan­osyl)‐6‐methyl‐1,2,4‐triazin‐5(2H)‐one, C₉H₁₄N₄O₄, the conformation of the N‐glycosidic bond is high‐anti and the 2‐deoxy­ribo­furan­osyl moiety adopts a North sugar pucker (²T₃). The orientation of the exocyclic C—C bond between the –CH₂OH group and the five‐membered ring is ap (gauche, trans). The crystal packing is such that the nucleobases lie parallel to the ac plane; the planes are connected via hydrogen bonds involving the five‐membered ring.     

4,1′,6′‐Trichloro‐4,1′,6′‐trideoxysucrose monohydrate

At 160 K, the gluco­pyran­osyl ring in 1,6‐di­chloro‐1,6‐di­deoxy‐β‐d ‐fructo­furan­osyl 4‐chloro‐4‐deoxy‐α‐d ‐gluco­pyran­oside monohydrate, C₁₂H₁₉Cl₃O₈·H₂O, has a near ideal ⁴C₁ chair conformation, while the fructo­furan­osyl ring has a ⁴T₃ conformation. The conformation of the sugar mol­ecule is quite different to that of sucralose, particularly in the conformation about the glycosidic linkage, which affects the observed pattern of intramolecular hydrogen bonds. A complex series of intermolecular hydrogen bonds links the sugar and water mol­ecules into an infinite three‐dimensional framework.     

8‐Aza‐7‐deaza‐2′‐de­oxy‐2‐(methyl­sulfan­yl)adenosine

In the title compound, 4‐amino‐1‐(2‐de­oxy‐β‐d ‐erythro‐pentofuranos­yl)‐6‐methyl­sulfanyl‐1H‐pyrazolo[3,4‐d]pyrimidine, C₁₁H₁₆N₅O₃S, the conformation of the glycosidic bond is between anti and high anti. The 2′‐deoxy­ribofuranosyl moiety adopts the C3′‐exo–C4′‐endo conformation (₃T⁴, S‐type sugar pucker), and the conformation at the exocyclic C—C bond is +sc (+gauche). The exocyclic 6‐amine group and the 2‐methyl­sulfanyl group lie on different sides of the heterocyclic ring system. The mol­ecules form a three‐dimensional hydrogen‐bonded network that is stabilized by O—H⋯N, N—H⋯O and C—H⋯O hydrogen bonds.     

7‐Deaza‐2′‐deoxy­guanosine

In the title compound, 2‐amino‐7‐(2‐deoxy‐β‐d ‐erythro‐pentofuran­osyl)‐3,7‐dihydro­pyrrolo[2,3‐d]pyrimidin‐4‐one, C₁₁H₁₄N₄O₄, the N‐glycosylic bond torsion angle, χ, is anti [−106.5 (3)°]. The 2′‐deoxy­ribofuran­osyl moiety adopts the ³T₄ (N‐type) conformation, with P = 39.1° and τ_m = 40.3°. The conformation around the exocyclic C—C bond is ap (trans), with a torsion angle, γ, of −173.8 (3)°. The nucleoside forms a hydrogen‐bonded network, leading to a close‐packed multiple‐layer structure with a head‐to‐head arrangement of the bases. The nucleobase interplanar O=C—C⋯NH₂ distance is 3.441 (1) Å.     

2,3,3′,6‐Tetra‐O‐acetyl‐4,1′,6′‐trichloro‐4,1′,4′,6′‐tetradeoxygalactosucrose

At 160 K, one of the Cl atoms in the furanoid moiety of 3‐O‐acetyl‐1,6‐di­chloro‐1,4,6‐tri­deoxy‐β‐d ‐fructo­furan­osyl 2,3,6‐tri‐O‐acetyl‐4‐chloro‐4‐deoxy‐α‐d ‐galacto­pyran­oside, C₂₀H₂₇­Cl₃O₁₁, is disordered over two orientations, which differ by a rotation of about 107° about the parent C—C bond. The conformation of the core of the mol­ecule is very similar to that of 3‐O‐acetyl‐1,4,6‐tri­chloro‐1,4,6‐tri­deoxy‐β‐d ‐tagato­furanos­yl 2,3,6‐tri‐O‐acetyl‐4‐chloro‐4‐deoxy‐α‐d ‐galacto­pyran­oside, particularly with regard to the conformation about the glycosidic linkage.     

2′,3′‐Dide­hydro‐3′‐deoxy­thymidine N‐methyl‐2‐pyrrolidone solvate (D4T·NMPO)

The title compound, 1‐(2′,3′‐di­deoxy‐β‐d ‐glycero‐pent‐2‐eno­furan­osyl)­thymine 1‐methyl‐2‐pyrrolidone solvate, C₁₀H₁₂N₂O₄·­C₅H₉NO, is an NMPO solvate of the anti‐AIDS agent D4T. In its crystal structure, both the pyrimidine and the furan­ose rings are planar and approximately perpendicular [82.1 (4)°]. The value of the torsion angle defining the orientation of the thymine with respect to the joined furane, χ = ?100.8 (4)°, and that of the torsion angle giving the orientation of the hydroxyl group linked to the furane ring, γ = 52.9 (5)°, show that the gly­cosyl­ic link adopts the so‐called high‐anti conformation and the 5′‐hydroxyl group is in the +sc position. The NMPO solvate is linked to the nucleoside through a fairly strong hydrogen bond.     

N8‐(2′‐O‐Methyl­ribofuranos­yl)‐8‐aza‐7‐deaza­adenine monohydrate

In the title compound, 4‐amino‐2‐(2‐O‐methyl‐β‐d ‐ribofuranos­yl)‐2H‐pyrazolo[3,4‐d]pyrimidine monohydrate, C₁₁H₁₅N₅O₄·H₂O, the conformation of the N‐glycosylic bond is syn [χ = 20.1 (2)°]. The ribofuran­ose moiety shows a C3′‐endo (³T₂) sugar puckering (N‐type sugar), and the conformation at the exocyclic C4′—C5′ bond is −ap (trans). The nucleobases are stacked head‐to‐head. The three‐dimensional packing of the crystal structure is stabilized by hydrogen bonds between the 2′‐O‐methyl­ribonucleosides and the solvent mol­ecules.     

2‐Amino‐7‐chloro‐2′‐deoxy­tubercidin

In 4‐chloro‐7‐(2‐de­oxy‐β‐d ‐erythro‐pento­furanos­yl)‐7H‐pyr­rolo­[2,3‐d]­pyrimidine‐2,4‐diamine, C₁₁H₁₄ClN₅O₃, the conformation of the N‐glycosylic bond is between anti and high‐anti [χ = −102.5 (6)°]. The 2′‐deoxy­ribofuranosyl unit adopts the C3′‐endo‐C4′‐exo (³T₄) sugar pucker (N‐type) with P = 19.6° and τ_m = 32.9° [terminology: Saenger (1989). Landolt‐Börnstein New Series, Vol. 1, Nucleic Acids, Subvol. a, edited by O. Madelung, pp. 1–21. Berlin: Springer‐Verlag]. The orientation of the exocyclic C4′—C5′ bond is +ap (trans) with a torsion angle γ = 171.5 (4)°. The compound forms a three‐dimensional network that is stabilized by four inter­molecular hydrogen bonds (N—H⋯O and O—H⋯N) and one intra­molecular hydrogen bond (N—H⋯Cl).     

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.     

8‐Aza‐7‐deaza‐7‐propynyladenosine methanol solvate

In the title compound, 4‐amino‐3‐propynyl‐1‐(β‐d ‐ribofur­anosyl)‐1H‐pyrazolo[3,4‐d]pyrimidine methanol solvate, C₁₃H₁₅N₅O₄·CH₃OH, the torsion angle of the N‐glycosylic bond is between anti and high‐anti [χ = −101.8 (5)°]. The ribofuranose moiety adopts the C3′‐endo (³T₂) sugar conformation (N‐type) and the conformation at the exocyclic C—C bond is +sc (gauche, gauche). The propynyl group is out of the plane of the nucleobase and is bent. The compound forms a three‐dimensional network which is stabilized by several hydrogen bonds (O—H·O and O—H·N). The nucleobases are stacked head‐to‐tail. The methanol solvent mol­ecule forms hydrogen bonds with both the nucleobase and the sugar moiety.     

2′‐Deoxy‐5‐fluorotubercidin

In the title compound, 4‐amino‐7‐(2‐deoxy‐β‐d ‐erythro‐pentofuranosyl)‐5‐fluoro‐7H‐pyrrolo[2,3‐d]pyrimidine, C₁₁H₁₃FN₄O₃, the conformation of the glycosyl bond lies between anti and high anti [χ = −101.1 (3)°]. The furanose moiety adopts the S‐type sugar pucker (²T₃), with P = 164.7 (3)° and τ = 40.1 (2)°. The extended structure is a three‐dimensional hydrogen‐bond network involving a C—H⋯F, two N—H⋯O and two O—H⋯O hydrogen bonds.     

1,N6‐Etheno derivative of 7‐de­aza‐2,8‐di­aza­adenosine

In the tricyclic nucleoside 7‐(β‐d ‐ribo­furan­osyl)‐7H‐imidazo­[1,2‐c]­pyrazolo­[4,3‐e][1,2,3]­triazine, C₁₁H₁₂N₆O₄, the con­formation of the N‐gly­cosyl bond is intermediate between anti and high anti [χ = −103.5 (3)°]. The ribo­furan­ose moiety adopts a ₃T² sugar pucker (S‐type sugar) and the conformation at the exocyclic C—C bond is ap (gauche–trans). Molecules of the title compound form a three‐dimensional network via three medium–strong intermolecular hydrogen bonds (one O—H⋯N and two O—H⋯O bonds).     

7‐Cyclopropyl‐2′‐deoxytubercidin: a carbocyclic side‐chain derivative of 7‐deaza‐2′‐deoxyadenosine

The title compound {systematic name: 4‐amino‐5‐cyclopropyl‐7‐(2‐deoxy‐β‐D‐erythro‐pentofuranosyl)‐7H‐pyrrolo[2,3‐d]pyrimidine}, C₁₄H₁₈N₄O₃, exhibits an anti glycosylic bond conformation, with the torsion angle χ = −108.7 (2)°. The furanose group shows a twisted C1′‐exo sugar pucker (S‐type), with P = 120.0 (2)° and τ_m = 40.4 (1)°. The orientation of the exocyclic C4′—C5′ bond is ‐ap (trans), with the torsion angle γ = −167.1 (2)°. The cyclopropyl substituent points away from the nucleobase (anti orientation). Within the three‐dimensional extended crystal structure, the individual molecules are stacked and arranged into layers, which are highly ordered and stabilized by hydrogen bonding. The O atom of the exocyclic 5′‐hydroxy group of the sugar residue acts as an acceptor, forming a bifurcated hydrogen bond to the amino groups of two different neighbouring molecules. By this means, four neighbouring molecules form a rhomboidal arrangement of two bifurcated hydrogen bonds involving two amino groups and two O5′ atoms of the sugar residues.     

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‐β‐d ‐arabinofuranosyl)‐7H‐pyrrolo[2,3‐d]pyrimidine, C₁₁H₁₃BrFN₅O₃, shows two conformations of the exocyclic C4′—C5′ bond, with the torsion angle γ (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 χ = −114.8 (4)°. The sugar pucker is N‐type (C3′‐endo; ³T₄), with P = 23.3 (4)° and τ_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).     

Solid‐state transformation of 4,2′‐an­hydro‐5‐(β‐d‐arabino­furan­osyl)­uracil dihydrate to 4,2′‐an­hydro‐5‐(β‐d‐arabino­furan­osyl)­uracil mono­hydrate

Crystals of 4,2′‐an­hydro‐5‐(β‐d ‐arabino­furan­osyl)­uracil, (I), obtained from an aqueous solution, were characterized as the dihydrate, C₉H₁₀N₂O₅·2H₂O, (Ia). In air, these crystals slowly transform to the mono­hydrate, C₉H₁₀N₂O₅·H₂O, (Ib), but remain crystalline. The solid‐state transformation proceeds with the loss of one water mol­ecule and a rearrangement of hydrogen‐bonded layers of mol­ecules. The furan­ose ring in (I) has an approximate C4′‐exo,O4′‐endo twist conformation. The central five‐membered ring is slightly puckered. The uracil group is planar within experimental uncertainty.