Highly effective transition structure designed catalyst for the enantio- and position-selective dihydroxylation of polyisoprenoids

[structure: see text] The chiral monocinchona derivative shown, synthesized in one step from two efficiently prepared chiral building blocks, was designed under mechanistic guidance as a catalyst for the enantio- and position-selective dihydroxylation of the terminal isopropylidene group of polyisoprenoids. Its efficacy as a synthetic reagent for this purpose was demonstrated for several different substrates.     

Linking cyano-bridged ladders by azide to form a layered metamagnet

Cyano-bridged corrugated ladder-like chains are connected by mu(1,1)-N(3) (end-on, EO) bridges to form a layered coordination polymer, [Mn(N(3))(CH(3)OH)[Cr(phen)(CN)(4)].CH(3)OH (2), which is the first mixed cyano-azide bridged compound, and shows metamagnetism below 21.8 K, a temperature much higher than that (3.4 K) of the crossed double chain [Cr(phen)(CN)(4)](2) [Mn(H(2)O)(2)].4H(2)O (1) based on the same building block [Cr(phen)(CN)(4)](-).     

Enzymatic reaction of the immobilized enzyme on porous silicon studied by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry

Desorption/ionization on silicon mass spectrometry (DIOS-MS) is a matrix-free technique that allows for the direct desorption/ionization of low-molecular-weight compounds with little or no fragmentation of analytes. This technique has a relatively high tolerance for contaminants commonly found in biological samples. DIOS-MS has been applied to determine the activity of immobilized enzymes on the porous silicon surface. Enzyme activities were also monitored with the addition of a competitive inhibitor in the substrate solution. It is demonstrated that this method can be applied to the screening of enzyme inhibitors. Furthermore, a method for peptide mapping analysis by in situ digestion of proteins on the porous silicon surface modified by trypsin, combined with matrix-assisted laser desorption/ionization-time of flight-MS has been developed.     

Novel synthesis of 2-oxo-3-butynoates by copper-catalyzed cross-coupling reaction of terminal alkynes and monooxalyl chloride

A general and efficient Cu(I)-catalyzed cross-coupling reaction of terminal alkynes and monooxalyl chloride for the synthesis of 2-oxo-3-butynoates and 2-oxo-3-butynoamides was developed. Readily available starting materials, the mild reaction conditions, wide functional group tolerance, and the obviation of stoichiometric organolithium or magnesium reagents combine to highlight this reaction.     

Adsorption voltammetry of the scandium-alizarin red S complex onto a carbon paste electrode

For the first time, a new method is described for the determination of scandium based on the cathodic adsorptive stripping of the scandium-alizarin red S complex onto a carbon paste electrode. The second-order derivative linear scan voltammograms of the complex are recorded by use of model JP-303 polarographic analyzer from 0.0 to -1.0 V (versus SCE). Optimum conditions are found to be: an acetic acid (0.36 mol l(-1))-potassium biphthalate (0.064 mol l(-1)) buffer solution (pH 4.0) containing 2.0x10(-5) mol l(-1) alizarin red S, a preconcentration potential of 0.0 V, a preconcentration time of 60 s, a rest time of 10 s and a scan rate of 100 mV s(-1). The results show that the complex can be adsorbed on the surface of a carbon paste electrode, yielding one peak at -0.58 V, corresponding to the reduction of alizarin red S in the complex at the electrode. The detection limit is found to be 6.0x10(-10) mol l(-1) for 3 min of preconcentration time. The linear range is 1.0x10(-9) to 4.0x10(-7) mol l(-1). Application of the procedure to the determination of scandium in the ore samples gave good results.     

以硫醚为主链的螯合树脂研究Ⅳ．含硫代硫酸根、叠氮基树脂的合成及吸附性能

聚环硫氯丙烷或环硫氯丙烷与环氧氯丙烷共聚物，在少量二乙烯三胺存在下制得交联预聚物，将交联预聚物分别与硫代硫酸钠，叠氮化钠反应，制得四种侧链带有硫代硫酸根或叠氮基的新型螯合树脂。它们对贵金属离子具有较高的吸附容量和较好的吸附选择性。     

A New Plate for Planar Electrochromatography

JPC – Journal of Planar Chromatography – Modern TLC - A new bonded RP-18 sintered silica gel plate for use in reversed-phase planar electrochromatography has been prepared in our...     

Quinine/selectfluor combination induced asymmetric semipinacol rearrangement of allylic alcohols: an effective and enantioselective approach to alpha-quaternary beta-fluoro aldehydes

A quinine/Selectfluor combination inducing rearrangement reaction of allylic alcohols was discovered, which involved a moderate yield with good enantioselective construction of alpha-quaternary carbon center and beta-fluoro aldehyde under base condition.     

Immunoaffinity Column Clean-Up and Liquid Chromatography with Post-Column Derivatization for Analysis of Aflatoxins in Traditional Chinese Medicine

A rapid tandem mass spectrometric (MS-MS) method for the quantification of gabapentin (GBP) in human plasma using 4-phenyl-4-aminobutanoic acid as an internal standard (IS) has been developed and validated. The drug and the internal standard were analyzed, by flow injection analysis without chromatographic separation, using a mobile phase of acetonitrile-water-formic acid (50:50:0.025, v/v/v) at a flow rate of 0.1 mL min^?1. The run-cycle time was <3 min injection-to injection. Quantitation was achieved using multiple reaction monitoring (MRM) scan at MRM transitions m/z 172 > 154 and m/z 180 > 117 for GBP and the IS, respectively. Ion suppression study indicated practically no suppressive effect of plasma constituents on the mass ions detection of GBP and IS, when measured in MRM scanning mode. Calibration curves were linear over the concentration range of 0.1–10 μg mL^?1 (r > 0.999) with a limit of quantification of 0.1 μg mL^?1 (RSD%; 7.6 and % DEVs; ?3.0 to +17.0%). Validation data showed that the RSD% values were in the range of 1.85 to 13.06%, whereas, the % DEVs values ranged from ?1.4 to +10.0% indicating good precision and accuracy. Analytical recoveries of GBP from spiked human plasma were in the range of 98.9 to 101.3%. On the other hand, recoveries of GBP from stored human plasma samples were in the range of 100.0 to 107.5% indicating that GBP was stable in plasma, with no appreciable degradation, when stored at ?20 °C. The developed method was applied for GBP monitoring in plasma samples of patients treated with GBP.     

Structural integration of tellurium oxide into mixed-network-former glasses: connectivity distribution in the system NaPO(3)-TeO(2).

Sodium phosphate tellurite glasses in the system (NaPO(3))(x)(TeO(2))(1-) (x) were prepared and structurally characterized by thermal analysis, vibrational spectroscopy, X-ray photoelectron spectroscopy (XPS) and a variety of complementary solid-state nuclear magnetic resonance (NMR) techniques. Unlike the situation in other mixed-network-former glasses, the interaction between the two network formers tellurium oxide and phosphorus oxide produces no new structural units, and no sharing of the network modifier Na(2)O takes place. The glass structure can be regarded as a network of interlinked metaphosphate-type P(2) tetrahedral and TeO(4/2) antiprismatic units. The combined interpretation of the O 1s XPS data and the (31)P solid-state NMR spectra presents clear quantitative evidence for a nonstatistical connectivity distribution. Rather, the formation of homoatomic P--O--P and Te--O--Te linkages is favored over mixed P--O--Te connectivities. As a consequence of this chemical segregation effect, the spatial sodium distribution is not random, as also indicated by a detailed analysis of (31)P/(23)Na rotational echo double-resonance (REDOR) experiments.