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1.
The reaction conditions for preparation of 6‐azido‐6‐deoxy‐glycoside remain elusive, although there are many successful cases in hand. After careful investigation of the reaction conditions, a practical procedure for the preparation of 6‐azido‐6‐deoxy‐galactopyranoside derivatives was demonstrated.  相似文献   

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An LC-ESI-MS method was developed for the identification and quantification of fructose-1,6-biphosphate (F1,6BP) and fructose-6-phosphate (F6P), respectively the substrate and the product of the enzymatic reaction catalysed by fructose-1,6-bisphosphatase (F1,6BPase). F1,6BPase, expressed predominantly in liver and kidney, is one of the rate-limiting enzymes of hepatic gluconeogenesis and has become a target for the development of new drugs for type 2 diabetes. The two sugar phosphates were separated on a Phenomenex Luna NH2 column (150 mm x 2.0 mm id) using the following mobile phase: 5 mM triethylamine acetate buffer/ACN (80:20) v/v in a linear pH gradient (from pH = 9 to 10 in 15 min) at the flow rate of 0.3 mL/min. The detection was performed with an IT mass spectrometer in negative polarity (full scan 100-450 m/z) and in SIM mode on the generated anions at m/z = 339 (F1,6BP) and m/z = 259 (F6P). Under the optimised final conditions, the method was validated for accuracy, specificity, precision (inter- and intradays RSD comprised between 1.0 and 6.3% over the range of concentrations used), linearity (50-400 microM), LODs (0.44 microM) and LOQs (1.47 microM), and the method was applied to F6P determination in the F1,6BPase catalysed hydrolysis of F1,6BP.  相似文献   

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Naturally occurring myo‐inositol was developed into a highly rigid diol by converting its 3,4‐ and 1,6‐vicinal diols in trans configuration into the corresponding butane‐2,3‐diacetals. The resulting diol bearing 6‐6‐6 fused ring system, in which conformational change is strictly suppressed, was combined with diisocyanates to perform polyadditions. The resulting polyurethanes were analyzed by differential scanning calorimetry, and it was found that their glass transition temperatures were much higher than those of the previously reported myo‐inositol‐derived polyurethanes, which were synthesized from a myo‐inositol‐derived diol bearing 5‐6‐5 fused ring system. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3798–3803  相似文献   

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Tang W  Muderawan IW  Ong TT  Ng SC 《Electrophoresis》2005,26(16):3125-3133
A novel single-isomer positively charged beta-cyclodextrin (beta-CD), mono-6(A)-butylammonium-6(A)-deoxy-beta-cyclodextrin tosylate (BuAM-beta-CD), has been synthesized, characterized, and used for the enantioseparations of alpha-hydroxy acids, carboxylic acids, and ampholytic analytes by capillary electrophoresis in acidic aqueous background electrolytes. The effective mobilities of all studied analytes decreased with increasing concentration of CD. Satisfactory resolutions were obtained for alpha-hydroxy acids over a wide range of chiral selector concentration. The optimum CD concentration was lower than 5 mM for the carboxylic acids, while higher than 20 mM for alpha-hydroxy acids. Inclusion complexation in combination with ion pair interaction seemed to account for the chiral discrimination process. The hydrogen bonding may provide secondary contribution for the chiral resolution of alpha-hydroxy acids. In addition, BuAM-beta-CD was further proved to be an effective chiral selector for anionic analytes by the baseline enantioseparation of a six-acid mixture within 20 min.  相似文献   

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Synthesis of stereoisomers of 6′‐mono‐ and 4′,6′‐di‐O‐benzyl cryptofolione is described through a key intermediate 6 , which was prepared by coupling of iodobenzene 8 with chiral propargyl alcohol 9 under Cosford protocol conditions. Monobenzyl ether 4 is obtained via epoxide 6 opening with vinyl Grignard, followed by cross‐metathesis reaction with a vinyl lactone 11 . Whereas, dibenzyl ether 5 is prepared by epoxide 6 opening with chiral propargyl alcohol 7 followed by simple transformations and finally cis‐Wittig olefination.  相似文献   

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SrNi10P6, EuNi10P6, and BaCo10As6: Phase Transitions and Crystal Structures SrNi10P6, EuNi10P6 and BaCo10As6 were prepared by heating mixtures of the elements in the range of 800°–1000 °C and were investigated by means of single‐crystal X‐ray methods. At higher temperatures the isotypic Ni phosphides (HT‐SrNi10P6: a = 6.481(2), b = 16.080(4), c = 8.763(2) Å (350 °C); HT‐EuNi10P6: a = 6.509(2), b = 16.063(4), c = 8.766(4) Å (500 °C)) crystallize in the BaNi10P6 type structure (Cmca; Z = 4), which can be described as an arrangement of Ni14P12 cages with Sr or Eu atoms in the centres. The cages are linked to layers separated by additional Ni atoms, which are coordinated tetrahedrally by P atoms of different cages. Cooling down both compounds undergo from about 270 °C (SrNi10P6) and 410 °C (EuNi10P6) respectively a second‐order phase transition involved with a change to an orthorhombic P lattice. In the structure of the NT phases (Pnma; Z = 4; NT‐SrNi10P6: a = 15.993(1), b = 6.473(1), c = 8.735(1) Å; NT‐EuNi10P6: a = 15.925(1), b = 6.478(1), c = 8.720(1) Å (25 °C)) the Ni14P12 cages are slightly distorted in comparison with the high temperature modifications. BaCo12As6 (a = 16.405(9), b = 6.858(4), c = 8.955(7) Å) crystallizes in the same structure (Pnma), but doesn't exhibit a comparable phase transition up to 600 °C. Measurements of the suszeptibiliy of EuNi10P6 between 4 K and 850 K showed divalent Europium and no magnetic order down to 4 K.  相似文献   

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Eucalyptol (1,8‐cineol), a cyclic monoterpenoid ether, is the dominant portion of eucalyptus oil, an essential oil of Eucalyptus globulus, accessible by steam distillation of its leaves. Some herbs and spices such as basil and cardamom also contain it as characterising flavour compound. Eucalyptus is a very diverse genus of Myrtaceae naturally occurring in Australia to whom the species have adapted in evolution. Planting Eucalyptus trees outside Australia has both benefits for poor populations and drawbacks. Especially, the enormous water consumption has been criticized. The total impact is doubtful. Eucalyptol is used in flavorings, fragrances, confectionery, cosmetics, cough suppressants, and insect repellents. Higher than normal doses are a hazard. A convenient isolation of eucalyptol from eucalyptus is reported. All analytical spectra were recorded and are reproduced and interpreted either in the main part or in the supporting information. The project is a follow up of the recent book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009).  相似文献   

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Chain‐folded lamellar crystals of the ten even‐even nylons: 6 6, 8 6, 8 8, 10 6, 10 8, 10 10, 12 6, 12 8, 12 10, and 12 12 have been grown from solution and their morphologies and structures studied using transmission electron microscopy, both imaging and diffraction. Sedimented mats were examined using X‐ray diffraction. The solution‐grown crystals are lath‐shaped lamellae and diffraction from these crystals, at room temperature, reveals that three crystalline forms are present in differing ratios. The crystals are composed of chain‐folded, hydrogen‐bonded sheets, the linear hydrogen bonds within which generate a progressive shear of the chains (p‐sheets). The sheets are found to stack in two different ways. Some p‐sheets stack with a progressive shear, to form the “αp structure”; others sheets stack with an alternate stagger, to form the “βp structure”. Both the αp and βp structures give two strong diffraction signals at spacings of 0.44 nm and 0.37 nm; these signals represent a projected intrasheet interchain distance (actual value 0.48 nm) and the intersheet spacing, respectively. Preparations of nylons 6 6, 8 6, 8 8, 12 6, and 12 8 consisted almost entirely of αp‐structure material, with only a trace of βp‐structure material being present. In contrast, nylons 10 6, 10 8, 10 10, 12 10, and 12 12 contained substantial quantities of both αp‐ and βp‐structure material, with αp‐structure material always being in the majority. Preparations of nylons 10 8, 12 10, and 12 12 also showed an additional diffraction signal at 0.42 nm; this signal is characteristic of the pseudohexagonal (high temperature) structure. The melting temperature of solution‐grown lamellae of these even‐even nylons decreases with decreasing linear amide density. On heating, the strong diffraction signals (0.44 nm and 0.37 nm) gradually moved together and merge at the Brill temperature to form a single diffraction signal (0.42 nm), characteristic of the pseudohexagonal structure. This single diffraction signal remained until melting. For nylons 6 6, 8 6, 8 8, 10 6, and 12 6, the Brill temperatures were substantially below the respective melting temperatures and the single 0.42 nm diffraction signal was stable over temperature ranges of 14 °C to 56 °C, depending on the nylon. Conversely, nylons 10 8, 10 10, 12 8, 12 10, and 12 12 had coincident melting and extrapolated Brill temperatures. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1209–1221, 2000  相似文献   

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The Unusual Transformation of P(SnMe3)3 to P4(SnMe2)6 The stannylated phosphine P(SnMe3)3 reacts in the presence of small amounts of [(ZnCl)2Fe(CO)4(THF)2] in THF (tetrahydrofurane) at room temperature forming insoluble P4(SnMe2)6 ( 1 ). This compound crystallizes as colourless needles directly from the reaction mixture (space group Cmcm, a = 1593.6(3) pm, b = 1118.2(2), c = 1602.5(3), Z = 4). Reaction of ZnCl2 with P(SnMe3)3 under the same reaction conditions leads to the complex [ZnCl2{P(SnMe3)3}THF] ( 2 ) (space group Pccn, a = 1593, 6(3) pm, b = 1118, 2(2), c = 1602, 5(3), Z = 8.  相似文献   

15.
It has been a long‐sought goal in cluster science to discover stable atomic clusters as building blocks for cluster‐assembled nanomaterials, as exemplified by the fullerenes and their subsequent bulk syntheses. 1 , 2 Clusters have also been considered as models to understand bulk properties, providing a bridge between molecular and solid‐state chemistry. 3 Because of its electron deficiency, boron is an interesting element with unusual polymorphism. While bulk boron is known to be dominated by the three‐dimensional (3D) B12 icosahedral motifs, 4 new forms of elemental boron are continuing to be discovered. 5 In contrast to the 3D cages commonly found in bulk boron, in the gas phase two‐dimensional (2D) boron clusters are prevalent. 6 8 The unusual planar boron clusters have been suggested as potential new bulking blocks or ligands in chemistry. 6a Herein we report a joint experimental and theoretical study on the [Ta2B6] and [Ta2B6] clusters. We found that the most stable structures of both the neutral and anion are D6h bipyramidal, similar to the recently discovered MB6M structural motif in the Ti7Rh4Ir2B8 solid compound. 9   相似文献   

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The efficient and effective storage of electrical energy with batteries is key for sustainable energy supply and emission free mobility. At present, lithium ion technology is the “best” high energy density battery and the first choice for use in electric vehicle applications, whereas for stationary storage of electricity a large number of battery technologies, including lithium ion batteries (LIB) , are in competition to each other. Even though the LIB is one step ahead of other battery technologies at the moment, this race is still open. Several new battery chemistries, such as lithium/sulfur, metal/air, sodium, magnesium and dual ion battery technologies are discussed as replacement or complementary technologies to lithium ion. The hope for improved and better battery technologies of the future is still high.  相似文献   

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Summary: The crystallization behavior of nylon‐6 and nylon‐6/montmorillonite nanocomposite films with different heat histories was investigated by wide‐angle X‐ray diffraction (WAXD). For nylon‐6 films isothermally crystallized above 170 °C or annealed at 200 °C and then quenched in ice water, a crystalline peak appeared at 2θ = 28.5°. This crystalline peak was strong in intensity for the former and weak for the latter. However, for nylon‐6 films cooled in air after isothermal crystallization or annealing, no crystalline peak at 2θ = 28.5° was observed in the WAXD patterns. For nylon‐6/montmorillonite nanocomposite films annealed above 140 °C, a crystalline double peak was observed between the α1 and α2 peaks. The possible origins of the peak at 2θ = 28.5° and the crystalline double peak are discussed.

WAXD patterns of isothermally crystallized nylon‐6/montmorillonite nanocomposite films.  相似文献   


18.
Thallium(18‐crown‐6) hexafluorophosphate was prepared and its structure was determined by X‐ray diffraction analysis. The Tl+ ion is surrounded by six oxygen atoms of 18‐crown‐6 and three fluorine atoms of , forming a sandwiched structure. If the three Tl–F interactions were considered significant, the coordination number in the title compound would be nine. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

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