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11.
Zhi-wei Ma Yu-xia Liu Li-juan Huo Xiang Gao Jing-chao Tao 《Tetrahedron: Asymmetry》2012,23(6-7):443-448
A novel class of chiral bifunctional thioureas bearing a chiral lipophilic beyerane scaffold and a tertiary amino group was designed and prepared. The thioureas were proven to be effective for catalyzing the doubly stereocontrolled asymmetric Michael addition between acetylacetone and nitroolefins. The corresponding adducts were obtained in high yields (up to 95%) and with good to excellent enantioselectivities (up to 97%). In addition, the reaction of tert-butyl acetoacetate and trans-β-nitrostyrene also proceeded smoothly with good enantioselectivity. 相似文献
12.
Triarylaminium salt was disclosed as a highly efficient nonmetallic initiator for the Friedel–Crafts reaction between chalcone epoxides and heteroarenes to construct a series of complex β-heteroaryl α-ketols in mild conditions and with good yields. Chalcone epoxides were presented as valuable halogen-free pre-electrophile in Friedel–Crafts alkylation through the formation of the stabilized benzylic cation intermediates. A plausible radical cation chain mechanism was also proposed. 相似文献
13.
In the present paper, we introduce some new subclasses of meromorphic starlike,convex, close-to-convex and quasi-convex functions of β-reciprocal in terms of the linear operator using subordination. We obtain the coefficient estimates, convolution properties, integral preserving properties and inclusion relationships of the classes. The results presented here include several results as their special cases. 相似文献
14.
The polyhydroxyurethane/attapulgite nanocomposites (PHU/ATP) were prepared by in-situ surface-initiated polymerization of a five-membered cyclic carbonate, 2, 2-bis [p-(1, 3-dioxolan-2-one-4-yl-methoxy) phenyl] propane (B5CC) and hexamethylene diamine, from the surface of the aminopropyl attapulgite nanoparticles (APATP) for the first time. The chemical grafting of the polymer on the surface of ATP was confirmed by FTIR and the morphology of the attapulgite nanoparticles in the nanocomposites was examined by TEM. The thermal stabilities of the polyhydroxyurethane (PHU) and the polyhydroxyurethane/attapulgite nanocomposites (PHU/ATP) were compared with thermogravimetric analysis (TGA).The %G of the attapulgite nanoparticles was also calculated from the results of TGA after the free polyhydroxyurethane was washed off. 相似文献
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Xiangyu Cao Ruihua Liu Jianli Liu Yapeng Huo Wei Yang Meng Zeng Chao Yang 《Applied biochemistry and biotechnology》2013,171(6):1444-1453
A novel polysaccharide [Lentinus edodes mycelia polysaccharide 2 (LMP2)] with a molecular weight of 2.27?×?104 Da was isolated from the Lentinus edodes mycelia and purified by Sephadex G-200 and diethylaminoethyl-32 column chromatography. HPLC results indicated that LMP2 contained mannose, arabinose, galactose, xylose, and rhamnose with a relative molar ratio of 1:0.74:3.23:1.18:10.98. Its antitumor activity was evaluated in vitro by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, colony formation assay, and transwell assay. LMP2 showed a remarkable inhibitory effect on the proliferation of Hep-2 cells, and at the concentration of 200 mg/ml, the inhibition ratio was 37.2 % after 72 h. Furthermore, colony formation of Hep-2 cells was reduced significantly after treatment with LMP2. Invasion of Hep-2 cells was inhibited significantly by LMP2. These results suggested that LMP2 could be explored as a potential antitumor material for laryngeal carcinoma. 相似文献
18.
Jiong Zhang Shuying Huo Hongmei Shi Shigang Shen Yanli Shang 《Transition Metal Chemistry》2013,38(1):15-20
The kinetics of oxidation of pyrrolidine by bis(hydrogenperiodato)argentate(III) complex anion ([Ag(HIO6)2]5?) was studied in alkaline medium, with reaction temperatures in the range of 15.0–30.0 °C. The experiments indicated that the oxidation follows an overall second-order reaction, being first-order in both Ag(III) and pyrrolidine. The observed second-order rate constants, k′, decreased with increasing [IO4 ?] but increased slightly with increasing [OH?]. The influence of ionic strength on the reaction rate was also investigated. The oxidation resulted in oxidative deamination of pyrrolidine, giving 4-hydroxybutyrate as the product. A reaction mechanism is proposed which includes an equilibrium between [Ag(HIO6)2]5? and [Ag(HIO6)2(OH)(H2O)]2?; these two Ag(III) species are reduced by pyrrolidine in parallel rate-determining steps. The rate equation derived from the proposed mechanism can explain the experimental observations. The rate constants of the rate-determining steps, together with the associated activation parameters, were calculated accordingly. 相似文献
19.
Analysis of an aggregation‐based algebraic two‐grid method for a rotated anisotropic diffusion problem 下载免费PDF全文
A two‐grid convergence analysis based on the paper [Algebraic analysis of aggregation‐based multigrid, by A. Napov and Y. Notay, Numer. Lin. Alg. Appl. 18 (2011), pp. 539–564] is derived for various aggregation schemes applied to a finite element discretization of a rotated anisotropic diffusion equation. As expected, it is shown that the best aggregation scheme is one in which aggregates are aligned with the anisotropy. In practice, however, this is not what automatic aggregation procedures do. We suggest approaches for determining appropriate aggregates based on eigenvectors associated with small eigenvalues of a block splitting matrix or based on minimizing a quantity related to the spectral radius of the iteration matrix. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
20.
Four cholate-based pyridinium compounds were synthesized and their binding abilities toward unmodified amino acids were investigated by UV spectroscopy and fluorescence emission spectroscopy. Studies revealed that the recognition process involved hydrogen bonding, electrostatic force, and π–π interaction. The receptor 4a was found to recognize l-tryptophan specifically, and the complex was studied by 1H NMR spectroscopy. The receptors 4b and 4c showed very little recognition ability toward l-tryptophan, indicating the important role of the benzyl group at pyridinium ring. 相似文献