Crystal structure of a nucleoside analogue, 2′,3′-dideoxy-3′-fluoro-5-chlorocytidine

The title compound, 1-(2,3-dideoxy-3-fluoro--d-erythro pentofuranos-1-yl)-5-chlorocytosine, crystallises in the orthorhombic space groupP2₁2₁2₁ witha=5.142(1),b=14.177(2),c=15.721(2) Å,Z=4. The crystal structure was solved by the heavy atom method and refined by full-matrix least-squares method to a finalR value of 0.031 for 1629 unique observed reflections. The N-glycosidic torsion angle is –156.1(2)° and the sugar moiety is anti to the cytosine base. The sugar pucker is ₂ ³ T withP=178.2(1)° and=31(1)°. The atom 05 is in a +sc conformation with respect to the furanose ring. The molecular packing in the crystal is stabilized by N-HN, N-HO, O-HO hydrogen bonds and C-HO close contacts.     

Crystal structure of a nucleoside analog: 2′,3′-dideoxy-3′-fluoro-5-bromocytidine

The title compound crystallizes in the orthorhombic space groupP2₁2₁2₁ witha=5.084(1),b=14.322(3),c=16.065(2)Å,Z=4. The structure was solved by the heavy atom method and refined by full-matrix least-squares calculations to a finalR value of 0.033 for 1106 unique observed reflections. The N-glycosidic torsion anglex has a value of –153.7(4)°, in the anti-range. The sugar pucker is²T₃ withP=175(1)° and=30(1)°. The C4-C5 conformation is + sc with =46.7(7)°. The structure is stabilized by N-HN, N-HO and O-HO hydrogen bonds and C-HO close contacts.     

Crystal and molecular structure of chloramphenicol analog: 2-amino-4-methoxy-2′,2′-dichloroacetophenone

The crystal and molecular structure of the title compound has been determined from diffractometric data usingMo K radiation. The crystals are orthorhombic, space groupP2₁2₁2₁, witha=12.052(3),b=11.901(2),c=6.976(1) Å andZ=4. The structure was solved by the heavy-atom method and refined by full-matrix least-squares to a finalR value of 0.039 with 1096 observed reflections. The molecule is is almost planar. The acetyl group and the phenyl ring are strongly conjugated, the corresponding dihedral angle being 3.3(2)°. The structure is stabilized by an intramolecular N(1)-H(N)1O(l) hydrogen bond.     

Crystal and molecular structure of 2′,4′-dimethoxyflavone

C₁₇H₁₄O₄,M _r =282.3, triclinic,P-1,a=8.469(3),b=8.516(2),c=20.425(8)Å,=84.95(3),=81.98(3), =70.47(2)°,V=1373(13)ų,Z=4,D _x =1.365 g cm^–3, (MoK )=0.71069 Å,=0.91 cm^–1,F(000)=592,T=294K,R=0.038 for 3577 observed reflections (F>3 (F)). The asymmetric unit is composed of two molecules. These two molecules, which are in planar conformations, differ in 4-methoxyl group orientation. Short intramolecular contacts are found between the -benzopyran portion and the dimethoxyphenyl ring.     

Crystal structure of 2,5-cyclohexadien-4-one-spiro-3′-(2′-methylthio-5′,5′-dimethyl-1′-pyrroline)

The crystal structure of the pyrrole derivative 2,5-cyclohexadien-4-one-spiro-3′-(2′-methylthio-5′,5′-dimethyl-1′-pyrroline) is determined by X-ray diffraction. Two independent molecules have similar structures and close geometric parameters but differ in configuration of the pyrrole ring and orientation of the thiomethyl group with respect to the pyrrole ring.     

Three-dimensional structure of thymidine phosphorylase from E. coli in complex with 3′-azido-2′-fluoro-2′,3′-dideoxyuridine

The three-dimensional structures of thymidine phosphorylase from E. coli containing the bound sulfate ion in the phosphate-binding site and of the complex of thymidine phosphorylase with sulfate in the phosphate-binding site and the inhibitor 3′-azido-2′-fluoro-2′,3′-dideoxyuridine (N₃F-ddU) in the nucleoside-binding site were determined at 1.55 and 1.50 Å resolution, respectively. The amino-acid residues involved in the ligand binding and the hydrogen-bond network in the active site occupied by a large number of bound water molecules are described. A comparison of the structure of thymidine phosphorylase in complex with N₃F-ddU with the structure of pyrimidine nucleoside phosphorylase from St. Aureus in complex with the natural substrate thymidine (PDB_ID: 3H5Q) shows that the substrate and the inhibitor in the nucleoside-binding pocket have different orientations. It is suggested that the position of N₃F-ddU can be influenced by the presence of the azido group, which prefers a hydrophobic environment. In both structures, the active sites of the subunits are in the open conformation.     

X-ray crystal and molecular structure of 2,3-dideoxy-4-thio-d-arabino-heptonic acid 1,4-lactone: a key intermediate for syntheses of 2′, 3′-dideoxy-4′-thio-l-nucleosides

The structure of 2,3-dideoxy-4-thio-d-arabino-heptonic acid 1,4-lactone has been determined by X-ray diffraction. Crystals of the compound are orthorhombic, space groupP2₁2₁2₁, with cell dimensionsa=11.555(5),b=10.451(5),c=9.604(5) Å, andZ=4. The diffraction experiment has allowed to assign the absolute configuration (4R, 5R, 6R) to the chiral centers of the molecule.     

Crystal structure of 2,2,3-trimethyl-3-(2′,4′,5′-tricyanophenyl) cyclopentyl-1-acetic acid, methyl ester, C20H21N3O2

The title compound crystallizes in space group P2₁/n, with a = 14.600(2), b = 7.091(2), c = 18.211(5) Å, and = 103.67(2)°. Owing to the centric space group, both C(1) and C(3) chiral centers are either R or S. The acetate group is equatorial, the H(1) and the methyl group at C(3) are axial and reciprocally trans.     

Crystal and molecular structure of 2-(2′-chloro-5′-nitrostyryl)benzoselenazole

The title compound C₁₅H₉ClN₂O₂Se (nsbse) is orthorhombic, witha=6.823(2),b=7.860(2),c=26.349(5) Å,Z=4,D _x =1.709,(MoK)=28.3 cm^–1,F(000)=720,T=298K in space groupP2₁2₁2₁. The structure was solved by heavy atom and Fourier methods and refined toR=0.045 for 1095 unique observed reflections. The molecule is almost planar, with a dihedral angle of 4.8(2)° between the benzoselenazole and phenyl rings. The C-Se-C angle in the selenazole ring is very small, 84.6(4)°, while the C-N-C angle in that ring is 113.7(7)°.     

Crystal structure of 2,4′-biflavonoid

The X-ray crystal structure of 2,4′-biflavonoid has been determined. Colorless regular prism shaped crystals of C₃₀H₂₂O₄ crystallize in the space group $P\bar 1$ with cell dimensionsa=11.574(1) Å,b=12.235(1) Å,c=17.428(1) Å, α=108.46(3)^o, β=80.08(1)^o, γ=103.34(2)^o,V=2264.7(4) ų, andZ=4.     

Crystal structure of 4-phenyl-3,5-dioxacyclohexyl-1, 1′-cyclopentane-2′,3″-(1,5,8,11-tetraoxacyclotridecane)

The structure of the title compound is determined by X-ray diffraction (DAR-UMB diffractometer, θ-θ/2θ scan mode, MoK _α radiation, direct method). The crystal is monoclinic, a = 24.582(6) Å, b = 22.812(8) Å, c = 8.647(3) Å, γ = 60.64(2)°, ρ _calcd = 1.232 g/cm³ space group A2/a, and Z = 8 for C₂₂H₃₂O₆. The molecule consists of four fragments: 13-crown-4 (A), 1,3-dioxane (B), a five-membered ring (C) acting as a bridge between fragments A and B, and a phenyl ring (D). Introduction of the bulky ring C as a bridge into the molecule results in significant deviations (up to ±0.014 Å) of the ether O atoms from planarity. The conformation of the macrocyclic fragment is [3433] according to the Dale notation. The C—H?O 1,4-interactions, which are energetically favorable occur in the propylene part of 13-crown-4: the C(2)?O(5) and C(4)?O(1) distances are 2.82 Å. The molecules in the structure form planar networks parallel to the xy plane. The intermolecular contacts correspond to the van der Waals interactions.     

Crystal structure ofβ-C.I. Solvent Yellow 18, 4(2′,4′-dimethylphenyl hydrazono)-5-methyl-2-phenyl-3H-pyrazol-3-one

The crystal structure of-C.I. Solvent Yellow 18, C₁₈H₁₈N₄O, has been determined by single crystal X-ray diffraction techniques. It crystallizes in the monoclinic system witha=30.948(18)Å,b=4.918(4)Å,c=20.861(9)Å,=91.68(4)°, space groupC2/c,Z=8. The structure has been solved by direct methods and least-squares refinement has been completed on three dimensional data (1237 reflections MoK radiation). The hydrogen atoms have been found but only their positional parameters refined. Final residual 0.092 (all intensity data). The molecule exists as the hydrazone tautomer and intramolecular hydrogen bonding keeps the molecule approximately planar. The molecules are packed in columns parallel to theb axis, while the molecule lies approximately parallel to the (51¯3) plane. The molecules are linked by van der Waals' force.     

Crystal structure of 5-(2′-aminophenyl)-2-dimethylamino-1,3,4-thiadiazole

The crystal structure of 5-(2′-Aminophenyl)-2-dimethylamino-1,3,4-thiazole is determined by X-ray diffraction. The compound is prepared by an unusual recyclization of 3-N, N-dimethylthioureidoquinazolin-4(3H)-one. The crystal is monoclinic, space group P2₁/c, a = 7.420(2) Å, b = 10.466(5) Å, c = 14.752(9) Å, β = 109.2(4)°, ρ_calcd = 1.359 g/cm³, and Z = 4 for the C₁₀H₁₂N₄S composition. The molecule consists of the thiadiazole and phenyl rings and the dimethylamine N(CH₃)₂ and amine NH₂ groups attached to the rings. The molecule as a whole is planar. The dihedral angle between the rings is 8.9°. The N(1) and N(4) atoms in the molecule are bound through the intramolecular interaction (2.76 Å). Molecules, which are linked in pairs by antiparallel hydrogen bonds, form a framework structure.     

Crystal and molecular structure of CI Solvent Yellow 18, 4-(2′,4′-dimethyl phenyl hydrazono)-5-methyl-2-phenyl-3H-pyrazol-3-one

The crystal structure of CI Solvent Yellow 18, C₁₈H₁₈N₄O, has been determined by single crystal X-ray diffraction techniques. It crystallizes in the monoclinic system witha=7.480(2) Å,b=19.184(3) Å,c=11.260(1) Å,=98.00(3)°, space groupP2₁/n andZ=4. The structure has been solved by direct methods, and least-squares refinement has been completed on three-dimensional data (2310 reflections, CuK radiation). The hydrogen atoms have been found, but only their positional parameters refined. Final residual 0.085 (all positive intensity data). The molecule exists as the hydrazone tautomer and intramolecular hydrogen bonding keep the molecule approximately planar. The molecules are packed in layers parallel to the (¯202) plane and in columns parallel tob. Alternate molecules within the columns are in antiparallel. The molecules are linked by van der Waals' forces.     

Crystal structure of bis-N,N′-p-chlorosalicylideneamine-1,2-diaminobenzene

The crystal structure of the title compound, C₂₀H₁₄N₂O₂Cl₂, has been determined by single crystal X-ray diffraction techniques. It crystallizes in the orthorhombic system witha=7.532(3)Å,b=18.563(2)Å,c=25.089(3)Å, space groupPbca,V=3507.9(3)ų,Z=8,F(000)=1584.D _x =1.459 g cm^–3,M=385.3 a. m. u., (MoK)=0.7107 Å, =3.35 cm^–1,T=297°K,R=0.086,R _w =0.049 for 2119 unique diffractometer data. The molecules are linked by van der Waals forces.     

X-ray structure of 3′,4-dimethylthio-3,4′-diquinolinyl sulfide

The title compound (C₂₀H₁₆N₂S₃) is monoclinic, witha=31.550(9),b=8.504(3),c=14.745(3) Å,=114.14(3)°,Z=8 and space groupC2/c. The structure was solved by direct methods and refined toR=0.038 for 3012 reflections. The molecule exists in an uncommon conformation. Two quinoline moieties are nearly perpendicular to each other (80.9(3)°). Both methylthio groups have different orientation (the 4-SCH₃ group is nearly perpendicular and the 3-SCH₃ is nearly coplanar to the quinoline moieties). Two pairs of sulfur atoms in ortho-positions remain in very close contact. The conformation of the molecule explains an unusual¹H NMR spectrum.Part XVI in the series of Azinyl Sulfides.     

Crystal structure ofcatena-O,O′-diethylphosphonoacetatotriphenyltin

Triphenyltin diethylphosphonoacetate, which crystallizes in the monoclinc space groupP2₁/c (a=15.154(4),b=9.159(3),c=17.685(4) Å, =91.410(8)°), adopts a polymeric structure in which planar triphenyltin cations (_C—Sn—C=357.3(6)°) are axially linked by the diethylphosphonoacetato anions (Sn–O_esteryl=2.129(3), SnO_phosphoryl=2.420(3) Å; O–SnO=171.9(1)° into chains that propagate by translations along theb-axis. The structure has been erfined toR=0.037 for 3384I3(I) reflections.     

Crystal structure of the meta hydroxyl phenyl analog of α(+)-prodine

The meta hydroxyphenyl analog of -prodine (1,3-dimethyl-(4-meta-hydroxy phenyl)-4-propionyloxypiperidine) free base crystallizes in the orthorhombic space group P2₁2₁2₁. The relative configuration of the compound shows the piperidine ring is in a chair conformation, the phenyl ring, the 3-methyl, and the N-methyl are equatorial, and the 4-propionyloxy group is axial. The molecular structure is similar to that of racemic -prodine and the potent opioid agonist, ketobemidone. There is a hydrogen bond between N(1) ... O(1) 2.79 Å.     

Crystal structure of 3,3′-dimethoxybenzydine (2-hydroxybenzal)diimine

Molecular and crystal structure of 3,3'-dimethoxybenzydine(2-hydroxybenzal)diimine, C₂₈H₂₄N₂O₄, have been determined by single crystal X-ray diffraction study. The title compound is monoclinic, with a= 18.045(2) Å, b= 11.725(4) Å, c= 12.436(6) Å, = 120.03(3)°, Z=4, D _x =1.32 g/cm³, (MoK) =0.089 mm^–1, and space group is C2/c. The structure was solved by direct methods and refined to a final R=0.056 for 2325 reflections with I > 2(I). There is half independent molecule in the asymmetric unit. The molecule has a twofold symmetry on the mid point of the C4 C4 ⁱ bond. The N1-C8 imine bond length of 1.284(3) Å is typical of a double bond. The molecule of the title compound is not planar. There is a strong intramolecular hydrogen bond between hydroxy oxygen atom and imine nitrogen atom. The crystal structure is stabilized by a weak intermolecular hydrogen bond of the C H O type forming three-dimensional cage.