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931.
Three new dammarane‐type triterpene saponins, 1 – 3 , together with three known compounds, 4 – 6 , were isolated from the aerial parts of Gynostemma pentaphyllum (Thunb.) Makino . By means of chemical and spectroscopic methods, their structures were established as (20S)‐3β,20,21‐trihydroxydammara‐23,25‐diene 3‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)] [β‐D ‐xylopyranosyl‐(1→3)]‐β‐D ‐glucopyranosyl‐21‐O‐β‐D ‐glucopyranoside ( 1 ), (20R,23R)‐3β,20‐dihydroxy‐19‐oxodammar‐24‐en‐21‐oic acid 21,23‐lactone 3‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)] [β‐D ‐xylopyranosyl‐(1→3)]‐α‐L ‐arabinopyranoside ( 2 ), and (21S,23S)‐3β,20ξ,21,26‐tetrahydroxy‐19‐oxo‐21,23‐epoxydammar‐24‐ene 3‐O‐[α‐L ‐rhamnopyranosyl‐(1→2)] [β‐D ‐xylopyranosyl‐(1→3)]‐α‐L ‐arabinopyranoside ( 3 ). 相似文献
932.
Jiang X Cao Y Wang Y Liu L Shen F Wang R 《Journal of the American Chemical Society》2010,132(43):15328-15333
Drug-lead synthesis through rapid construction of chiral molecular complexity around the biologically relevant framework using a highly efficient strategy is a key goal of organic synthesis. Molecules bearing a spirooxindole-type framework exhibit important bioactivities. Herein, we present a highly efficient and convenient strategy that allows rapid construction of unique optically active spiro[oxazoline-3,3'-oxindole]s through the organocatalyzed asymmetric synthesis of spirocyclic thiocarbamates via an aldol reaction. Preliminary biological evaluation of several of the spirooxazolines using a model of acute neuroinflammation revealed promising antipyretic activity and provided an opportunity to discover new antipyretic agents. 相似文献
933.
Liu YL Wang BL Cao JJ Chen L Zhang YX Wang C Zhou J 《Journal of the American Chemical Society》2010,132(43):15176-15178
We report a highly enantioselective Morita-Baylis-Hillman (MBH) reaction of isatins and acrolein to provide enantiomerically enriched 3-substituted 3-hydroxyoxindoles, which could serve as valuable synthetic building blocks. This is also the first time that a ketone has been used as the electrophile and acrolein as the nucleophile in a highly enantioselective catalytic asymmetric MBH reaction. Hatakeyama's catalyst, β-isocupreidine (1), turned out to be a powerful catalyst for this transformation. 相似文献
934.
Shouwen Jin Dr. Daqi Wang Zhiwen Zheng Jie Chen Chao Feng Xianghua Ye Yiping Zhou 《无机化学与普通化学杂志》2010,636(8):1617-1624
Five novel coordination polymers, [(Cu(L1)2OH) · Cl · 3H2O] ( 1 ) [L1 = bis(N‐imidazolyl)methane], [Cd(L1)2(NCS)2] ( 2 ), [Zn(L1)2(NCS)2] ( 3 ), [Cu(L1)2(NO3)2] ( 4 ), and [Cu(L2)1.5(NCS)2] ( 5 ) [L2 = 1,4‐bis(N‐imidazolyl)butane] were obtained from self‐assembly of the corresponding metal salts with flexible ligands and their structures were fully characterized by X‐ray diffraction (XRD) analysis, Fourier Transform Infrared (FT‐IR) spectroscopy, elemental analysis and thermogravimetric (TGA) measurements. X‐ray diffraction analyses revealed that complexes 1 , 2 , 3 , and 4 exhibit 1D double‐stranded chain structures, which result from doubly bridged [CuOH], [M(NCS)2] (M = Cd, Zn), and [Cu(NO3)2] units, respectively. The polymeric copper complex 5 displays 1D ladder structure., These complexes, with the exception of complex 1 , are stable up to 300 °C. 相似文献
935.
A method for flow injection with chemiluminescence (CL) detection has been developed for the determination of proteins. It is based on the luminescence of the N-bromosuccinimide-fluorescein-protein system, where fluorescein is used as an energy transfer reagent in alkaline medium. The CL of the system is strongly enhanced by hexadecyl trimethyl ammonium bromide. Optimum conditions and possible mechanisms have been investigated. Under optimum experimental conditions, the linear range is from 0.4 to 40 µg·mL?1 for egg albumin, 0.2 to 20 µg·mL?1 for bovine serum albumin, and from 1 to 100 µg·mL?1 for bovine hemoglobin. The detection limits are 37, 62, and 240 ng·mL?1, respectively. 相似文献
936.
Yan Li Peng Wang Xin Wang Ming Cao YunSheng Xia Chun Cao MeiGui Liu ChangQing Zhu 《Mikrochimica acta》2010,169(1-2):65-71
A method for determination of vitamin B1 has been developed that is based on the enhancement effect of vitamin B1 on the luminescence of water-soluble CdTe nanorods modified with thioglycolic acid and cysteine. The effect of variables including the size of the nanorods on the enhancement of luminescence have been investigated. A preliminary mechanistic study showed that the passivating action of vitamin B1 on the surface of the CdTe nanorods is likely to be responsible for the enhancement. Interferences by shortwave fluorescence are effectively eliminated because measurements are performed in the near-infrared. Due to the near-infrared measurement character, the fluorescence interference of vitamin B2 can be effectively eliminated. Under the optimum conditions, the extent of luminescence enhancement is proportional to the concentration of vitamin B1 in the range from 0.1 to 3.0 μmol L?1 and the detection limit is 0.03 μmol L?1. The relative standard deviation for 2.0 μmol L?1 vitamin B1 is 1.3% (n?=?6). The method is highly sensitive and selective, avoids the sample treatment needed in other procedures, and can be applied to the determination of vitamin B1 in real samples with satisfactory results. 相似文献
937.
Zhihua Jia Xiaoli Zhang Yaling Zhao Xuejun Cao 《Applied biochemistry and biotechnology》2010,160(7):2014-2025
Feedback inhibition existed in lovastatin biosynthesis from Aspergillus terreus. Exogenous lovastatin and other different polyketide antibiotics biosynthesized by polyketide synthase were supplemented
to the cultures of A. terreus to investigate their influences on lovastatin production. Supplementing exogenous lovastatin of 100 mg l−1 at the early stage of fermentation and the fast stage of its biosynthesis resulted in decreases of 76.4% and 20% in final
lovastatin production, respectively. However, the fungal cell growth was not affected; the growing cycle was only prolonged
in the submerged cultivation. Separate supplementation of the five kinds of polyketide antibiotics such as tylosin, erythromycin,
tetracycline, daunorobin, and rifamycin to the cultures resulted in increases of about 20~25% in the final lovastatin production.
Especially, supplementing tylosin of 50 mg l−1 at the beginning of lovastatin biosynthesis led to the final lovastatin production of 952.7 ± 24.3 mg l−1, which was improved by 42% and 22% compared with that produced in the control and the original culture, respectively. These
results are helpful to understand the regulations on lovastatin biosynthesis and improve the final desired metabolite contents
in many antibiotics production. 相似文献
938.
Formation of the SEI layer on Si–Cu film electrode in the ionic liquid electrolyte of 1 M lithium bis(trifluoromethylsulfonyl)imide/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (LiTFSI/MPP-TFSI) was investigated using ex-situ ATR FTIR and X-ray photoelectron spectroscopy. The SEI layer is found to be composed of organic and inorganic compounds that are the decomposition products of MPP cation and TFSI anion, and effectively passivate the electrode surface during initial cycling. Formation of a stable SEI layer leads to an excellent capacity retention 98% of the maximum discharge capacity, delivering discharge capacities of > 1620 mAhg? 1 over 200 cycles. The data contribute to a basic understanding of SEI formation and composition responsible for the cycling performance of Si-based alloy anodes in ionic liquid electrolyte-based rechargeable lithium batteries. 相似文献
939.
Shao Rong Luan Yi Hua Zhu Yu Qing Jia Qing Cao 《Journal of Thermal Analysis and Calorimetry》2010,99(2):523-530
A complex of thiourea and bismuth trichloride has been synthesized. Its composition is Bi3Cl9[SC(NH2)2]7. Crystallographic data are a = 7.141(2) Å, b = 8.820(3) Å, c = 16.365(5) Å, α = 99.389(4)°, β = 95.422(4)°, γ = 106.177(4)°, triclinic system. There are the mononuclear anion [BiCl5SC(NH2)2]2? and the dinuclear cation {Bi2Cl4[SC(NH2)2]6}2+ with the Bi–Cl–Bi bridge bonds in the complex. The electric conductance of the absolute methanol solution contained the complex indicates that the complex is an ionic compound. Raman spectra indicate that the bismuth ion is coordinated by the sulfur atoms of the thiourea. The thermal analysis verifies the structure of complex. The TG–MASS curves show the structure rearrangement in the complex at about 118 °C. The DSC curves and calculation means that the structure rearrangement is irreversible. 相似文献
940.
Xiao-Hong Cao Li-Xiang Zhang Wei-Peng Cai Yao-Qun Li 《Electrochemistry communications》2010,12(4):540-543
A single-walled carbon nanotube (SWNT) is covalently attached to the interior surface of a conical glass micropore electrode (GME) to create a novel amperometric dopamine sensor (SWNT/NH-GME). The SWNT/NH-GME combines the advantages of excellent transport properties of the cone-shaped micropore with the characteristics of a SWNT, exhibiting a dramatic electrocatalytic effect on the oxidation of dopamine (DA). Cyclic voltammetry and amperometric methods were employed to study the electrochemical behavior of the SWNT/NH-GME. The results showed that the SWNT/NH-GME sensor exhibited an excellent immunity from ascorbic acid interference and was able to measure DA concentrations with a detection limit of 4.2 × 10?7 mol/L (S/N = 3). 相似文献