A Novel Boron-Rich Scandium Borocarbide; Sc4.5−xB57−y+zC3.5−z(x=0.27, y=1.1, z=0.2)

A novel ternary boron-rich scandium borocarbide Sc_4.5−xB_57−y+zC_3.5−z (x=0.27, y=1.1, z=0.2) was found. Single crystals were obtained by the floating zone method by adding a small amount of Si. Single-crystal structure analysis revealed that the compound has an orthorhombic structure with lattice constants of a=1.73040(6), b=1.60738(6) and c=1.44829(6) nm and space group Pbam (No. 55). The crystal composition ScB_13.3C_0.78Si_0.008 calculated from the structure analysis agreed with the measured composition of ScB_12.9C_0.72Si_0.004. The orthorhombic crystal structure is a new structure type of boron-rich borides and there are six structurally independent B₁₂ icosahedra I1—I6, one B₈/B₉ polyhedron and nine bridging sites all which interconnect each other to form a three-dimensional boron framework. The main structural feature of the boron framework structure can be understood as a layer structure where two kinds of boron icosahedron network layer L1 and L2 stack each other along the c-axis. There are seven structurally independent Sc sites in the open spaces between the boron icosahedron network layers.     

Reaction of diazoalkanes with unsaturated compounds. 11. Relative reactivity of olefins on catalytic cyclopropanation with diazomethane and palladium catalysts

The relative reactivity of unsaturated compounds on catalytic cyclopropanation with diazomethane in the presence of catalysts based on Pd²⁺ [Pd(OAc)₂, Pd(acac)₂, (PPh₃)₂·PdCl₂] has been studied using competing reactions. An interconnection was shown between the relative reactivity of the olefins and the coordinating activity of the C=C bond depending on its strain and spatial environment.For previous communication, see [1].Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 450054 Ufa; N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2353–2361, October, 1992.     

Synthesis and anti-HIV activity of l-β-3′-C-cyano-2′,3′-unsaturated nucleosides and l-3′-C-cyano-3′-deoxyribonucleosides

An efficient synthetic method was developed for l-β-3′-C-cyano-2′,3′-unsaturated nucleosides and l-3′-C-cyano-3′-deoxyribonucleosides. The key intermediate 11 was obtained from l-xylose, from which a series of pyrimidine and purine nucleosides were prepared in high yield by the coupling of 11 and various silyl-protected bases in the presence of TMSOTf. These nucleosides were eliminated, followed by deprotecting to give l-β-3′-C-cyano-2′,3′-unsaturated nucleosides. When selectively deprotected by hydrazine hydrate in buffered acetic acid-pyridine followed by treatment with potassium carbonate in methanol, l-3′-C-cyano-3′-deoxyribonucleosides were obtained. The synthesized nucleosides were tested for anti-HIV activity.     

A Novel Approach to Synthesis of α，β－Unsaturated Ketones

A new approach to the synthesis of α，β-unsaturated ketones from 1,2,3-trimethyl benzimidazolium salt via the condensation reaction with aldehydes followed by the addition reaction of Grignard reagents with quaternary C=N bond was provided.     

由4，4＇-联二吡啶桥联α,β-不饱和酸铜形成铜（II）的一维配位聚合物

A methanol solution of 4,4‘-bipyridine reacts with Cu2A4(H2O)2 to yield coordination polymers of general formula: [Cu2A4(bipy)]n [A: CH2=C(Me)CO2^- (1), CH2=CHCO2^- (2); bipy: 4,4‘-bipyridine]. They were characterized by elemental analyses, IR spectra and thermal analyses. The X-ray structure analyses of 1 show a one-dimensional chain structure where the binuclear structural units Cu2[CH2=C(Me)CO2]4 are bridged by 4,4‘-bipyridine molecules. Furthermore, the binuclear units between adjacent layers can form micropores. The temperature-dependent magnetic susceptibility of 1 indicates that the strong antiferromagnetic interaction exists between copper(Ⅱ) atoms in the binuclear units.     

Comparison of methanol and acetonitrile as solvents for the separation of sertindole and its major metabolites by capillary zone electrophoresis

Sertindole (1-[2-[4-[5-chloro-1-(4-fluorophenyl)-1H-indol-3-yl]-1-piperidinyl]ethyl]-2-imidazolidinone), an atypical antipsychotic drug, was separated by capillary electrophoresis from its two main metabolites norsertindole and dehydrosertindole. The low solubility of the analytes in water (octanol-water partition coefficient is about 10(5)) is overcome by the use of methanol (MeOH) and acetonitrile (ACN) as solvents for the background electrolyte (BGE). Mobilities were measured in BGEs with defined pH in a broad range. It was found that in MeOH the mobility of the analytes is mainly governed by acid-base equilibria, whereas in ACN other reactions like ion pairing and homo-conjugation play a pronounced role and lead to a complex pattern of the mobility as function of the pH. However, separation can be obtained in less than 10 min in both solvent systems.     

Enantiomer Separation of the Four Stereoisomers of 1-(4-Hydroxy-3-Methoxy)-Phenyl-2-[4-(1,2,3-Trihydroxy-Propyl)-2-Methoxy]-Phenoxy-1,3-Propandiol from Hydnocarpus annamensis by Capillary Zone Electrophoresis with HP-β-CD as Chiral Selector

A capillary zone electrophoresis method with HP-β-CD as chiral selector was established for the chiral separation of four stereoisomers of 1-(4-hydroxy-3-methoxy)-phenyl-2-[4-(1,2,3-trihydroxy-propyl)-2-methoxy]-phenoxy-1,3-propandiol for the first time, which were isolated from Hydnocarpus annamensis. The effects of chiral selector type and concentration, buffer composition, pH and concentration, and cartridge temperature on the enantioseparation were investigated. A baseline separation of the four stereoisomers was achieved in less than 18 min under the optimized conditions: 40 mmol L⁻¹ Borax–NaOH buffer (pH 10.02) in the presence of 100 mmol L⁻¹ HP-β-CD at 15°C and 30 kV. The experimental results showed that the method by capillary zone electrophoresis for the separation of four stereoisomers is powerful, sensitive and fast, requires less amounts of reagents, and can be employed as a reliable alternative to other methods.     

Field-amplified sample injection and in-capillary derivatization for capillary electrophoretic analysis of metal ions in local wines

In-capillary derivatization and field-amplified sample injection (FASI) coupled to capillary zone electrophoresis (CZE) was evaluated for the analysis of metals (Co(II), Cu(II), Ni(II), and Fe(II)) using 2-(5-Nitro-2-Pyridylazo)-5-(N-Propyl-N-Sulfopropylamino)Phenol (Nitro-PAPS) as the derivatizing agent. For FASI, the optimum conditions were water as sample solvent, 1 s hydrodynamic injection (0.1 psi) of a water plug, 5 s of electrokinetic introduction (10 kV) of the sample. The in-capillary derivatization was successfully achieved with zone-passing strategy in order tandem injection of Nitro-PAPS reagent (0.5 psi, 7 s), a small water plug (0.1 psi, 1 s), and metal ion introduction (10 kV, 5 s). The solution of 45 mmol L^− 1 borate pH 9.7 and 1.0 × 10^− 5 mol L^− 1 Nitro-PAPS containing 20% acetonitrile was used as the running buffer. The limit of detection obtained by the proposed method was lower than those from pre-capillary derivatization about 3–28 times. The recovery of the method was comparable to pre-capillary derivatization method. In-capillary derivatization-FASI-CZE was applied to analysis of metals in wine samples. The results were compared with those obtained by CZE with pre-capillary derivatization method and atomic absorption spectrometry (AAS).     

Comparative study of capillary zone electrophoresis and micellar electrokinetic chromatography for the separation of twelve aromatic sulphonate compounds

Summary Two modes of capillary electrophoresis (CE), capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC), were investigated for the separation of 12 aromatic sulphonate compounds. In CZE, although the voltage applied, the buffer concentration and the pH were optimized for effective separation of the compounds studied, under the best conditions four of the five amino compounds coeluted, as did naphthalene-1-sulphonic acid and naphthalene-2-sulphonic acid. In MEKC, sodium dodecyl sulphate (SDS) and Brij 35 were chosen as the anionic and nonionic surfactants and the effect of the concentration of micelles was examined. The effect of adding methanol as the organic modifier was also investigated with each of these micellar systems. All the analytes, including the isomers, were completely separated by use of MEKC with Brij 35 but when SDS was used only 11 compounds were separated because two amino compounds coeluted.     

Analysis of chlortetracycline and related substances by capillary zone electrophoresis: Development and validation

Summary A capillary zone electrophoresis method has been developed and validated for the analysis of chlortetracycline and related substances. The influence of the type of buffer, pH and concentration of the buffer were investigated. In all cases 1 mM EDTA was added to prevent metal ion complexation. Instrumental parameters such as capillary temperature and applied voltage were optimised. The following methods is proposed: capillary: fused silica, 44 cm (36 cm effective length), 50 μm i.d.; buffer: 120 mM sodium tetraborate including 1mM EDTA at pH 8.5; voltage: 10 kV; temperature: 25°C; detection wavelength: 280 nm. The robustness of the method has been examined by means of a full-fraction factorial design. The parameters for validation namely relative standard deviation, linearity, precision, limit of detection and limit of quantitation are also reported.