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131.
Some new N‐glycosides of 4‐(2‐phenylethyl)‐5‐pyridyl‐1,2,4‐triazole‐3‐thiones were synthesised by the coupling reaction of halo sugar with 4,5‐disubstituted 3H‐1,2,4‐triazole‐3‐thiones in the presence of mercuric cyanide and dry nitromethane as solvent, followed by deprotection using dry ammonia in methanol. All of the above compounds were fully characterized by means of infrared, 1H NMR spectroscopy, mass spectroscopy and elemental analysis. 相似文献
132.
D. V. Shishkin E. R. Mukhamed’yarova N. Z. Baibulatova V. A. Dokichev Yu. V. Tomilov 《Chemistry of Natural Compounds》2007,43(3):293-297
Diastereomers of N-(2-(1-adamantyl)-2-hydroxyethyl)cytisine were synthesized by reduction of N-(2-(1-adamantyl)-2-oxoethyl)cytisine with NaBH4. Their structures were established using x-ray structure analysis.
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Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 244–247, May–June, 2007. 相似文献
133.
《Electroanalysis》2003,15(1):19-25
The electrochemical behavior of 2‐(5‐amino‐ 1,3,4‐oxadiazolyl)‐5‐nitrofuran (NF359) and its comparison with well‐known drugs such as nifurtimox (NFX) and nitrofurazone (NFZ) in protic, mixed and aprotic media by cyclic voltammetry, tast and differential pulse polarography was studied. All the compounds were electrochemically reducible in all media being the reduction of the nitrofuran group the main voltammetric signal. The one‐electron reduction couple due to the nitro radical anion formation was visualized in mixed (for NF359 and NFZ) and aprotic media (for all compounds). By applying a cyclic voltammetric methodology we have calculated the decay constants (k2) of the corresponding nitro radical anions in mixed and aprotic media. In mixed medium data fit well with a disproportionation reaction of the nitro radical anion but in aprotic medium fit better with a dimerization reaction. Also, considering cyclic voltammetric measurements in aprotic media we have estimated the reduction potential of the RNO2/RNO2.? couple in aqueous medium, pH 7 (E17 values) finding very good correlation with E17 values obtained by pulse radiolysis. Furthermore we have calculated the equilibrium constants from the electron transfer from nitro radical anion to oxygen (kO2) finding that nitro radical anion from NF359 is thermodynamically favored to react with oxygen in respect to both NFZ and NFX. 相似文献
134.
A highly atom-efficient synthetic protocol for hydroarylation of terminal-aryl alkynes and styrene through the regioselective CC bond formation via the electrophilic addition of naphthols and substituted phenols has been developed using alumina-sulfuric acid as a heterogeneous supported solid acid catalyst. This methodology shows excellent regioselectivity and affords the desired product in good to excellent yield. The heterogeneous catalyst can also be recycled efficiently without much loss of activity. 相似文献
135.
T. M. Polyanskaya 《Journal of Structural Chemistry》2006,47(5):887-893
A single crystal X-ray diffraction study of a new iodine-containing cluster compound 9-(pyridine)-11-iodo-decahydro-7,8-dicarba-nido-undecaborane [9-C5H5N-11-I-7,8-C2B9H10] has been performed. Crystal data: C7H15B9NI, M = 337.39, monoclinic, space group P21/c, unit cell parameters: a = 9.348(1) Å, b = 11.159(1) Å, c = 13.442(2) Å, β = 98.13(1)°, V = 1388.1(5) Å3, Z = 4, d calc = 1.614 g/cm3, T = 295 K, F(000) = 648, μ = 2.276 mm?1. The structure was solved by a direct method and refined in the full-matrix anisotropic approximation (isotropic for hydrogen atoms) to final agreement factors R 1 = 0.0254, wR 2 = 0.0454 for 2437 I hkl ≥ 2σI from 3590 measured I hkl (an Enraf-Nonius CAD-4 diffractometer, λMoK α , graphite monochromator, θ/2θ-scanning). The molecules are joined into a supramolecular assembly by hydrogen bonds X-H?I (X = B, C). 相似文献
136.
137.
Wen Weng Qing Le Zeng Bi Xia Yao Wen Shi Lin Qing Hua Wang Xiu Li You 《Chromatographia》2006,64(7-8):463-467
Five structurally related amino acid derivatives were enantioseparated by HPLC with a commercially available chiral stationary phase, Chiralcel OD-H. The chromatographic experiments were performed in the normal phase mode. n-Hexane/polar alcohol was used as mobile phase. Excellent baseline enantioseparations could be obtained for all these solutes. The effects of the concentration of polar alcohol and the column temperature on the retentions and enantioseparations were studied in detail. From the van't Hoff plots the corresponding apparent thermodynamic parameters were derived. Mechanism aspects of chiral recognition were discussed based on the relationship between the thermodynamic parameters and the structures of the solutes. It was found that the substituent of the phenyl group on the residual group of the amino acid derivatives was close relevant to thermodynamic origin of enantioseparation. Much better enthalpy–entropy compensation effect was obtained by plotting the differential, rather than the original, thermodynamic parameters. 相似文献
138.
Valle-Algarra FM Medina A Gimeno-Adelantado JV Llorens A Jiménez M Mateo R 《Talanta》2005,66(1):194-201
Various solid-phase extraction (SPE) procedures for clean-up, two perfluoroacylation reagents (pentafluoropropionic anhydride (PFPA) and heptafluorobutyric anhydride (HFBA)) and two chromatographic columns (HP-1701 and HP-5) have been assessed comparatively to achieve the determination of type B trichothecenes (deoxynivalenol (DON), nivalenol (NIV), 3- and 15-acetyldeoxynivalenol (3- and 15-ADON)) in wheat grain by gas chromatography (GC)-electron-capture detection (ECD). Spiked wheat samples were extracted with acetonitrile-water (84:16, v/v). Tested SPE procedures were MycoSep 225 column, Florisil and different cartridges prepared in the laboratory with mixtures of various sorbents like alumina, Celite 545, C18, silica and charcoal. We propose MycoSep 225 column, and cartridges made with alumina-charcoal-silica and alumina-charcoal-C18 silica mixtures as clean-up procedures on the basis of recovery values (89.6, 87.3 and 86.1% for deoxynivalenol, respectively, at 1.0 mg/kg spiking level). The two last procedures are less expensive. Pentafluoropropionic anhydride was more stable against moisture and less expensive, while recoveries were similar to those obtained with heptafluorobutyric anhydride. HP-1701 column can separate 3- and 15-acetyldeoxynivalenol derivatives while HP-5 cannot, although this last column provided lower bleed and better sensitivity. 相似文献
139.
Photoelectron Spectra and Molecular Properties. 133. Trifluoromethyldisulfane and Derivates F3CSSX (X?CF3, F, Cl, Br) The He(I) photoelectron spectra of trifluoromethyldisulfane F3CSSH and its derivatives F3CSSX (X?CF3, F, Cl, Br) are assigned by Koopmans correlations, IE = ?ε, with MNDO eigenvalues and by radical cation state comparison. Of special interest are the n/n splittings, which amount to 1.15 eV F3C? SS? F or 0.87 eV in F3? SS? Cl, and the dependance of which on the dihedral angle ω(XS? SX), on the SS bond length and on the acceptor effect of the F3C substituents is discussed. 相似文献
140.
An efficient method for N-alkylation of diethyl acetamidomalonate (DEAM) is reported. C-Alkenylation was achieved by treating the N-alkenylated DEAM with various electrophiles in the presence of Cs2CO3. RCM reactions of C- and N-alkenylated products gave cyclic amino acid derivatives in good yields. 相似文献