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11.
α-Aryl-α-aminocarbonyloxime O-pentafluorobenzoates are found to be promising precursors for synthesis of 2,3-disubstituted indole derivatives catalyzed by PdCl2(MeCN)2 in the presence of MgO as a base. The reaction is supposed to proceed via intramolecular aromatic C-H amination of a vinyl nitrene-palladium intermediate. 相似文献
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This paper describes a rapid technique for reconstruction of the internal area function of a duct using blockage-induced eigenvalue shifts determined from eigenfrequencies measured under two sets of duct termination boundary conditions. A single broad band maximum length sequence (MLS) measurement of short duration is utilized to obtain the transfer function of the duct, which in turn can be utilized to determine its eigenvalue shifts and subsequently its internal area function using an inverse perturbation technique. The reconstruction results display the same order of accuracy as those obtained previously using swept sine measurements of extended duration. An expression for the determination of the area function is presented utilizing resonant frequency information alone, thus rendering duct length determination unnecessary. A computational routine further simplifies the process such that the accuracy of the technique could be ascertained for a range of configurations including longer ducts and ducts that initially have nonuniform internal cross section over their length. Development of a relationship between obstacle length and wavelength of the lowest eigenfrequency required for successful reconstruction is also described. This is an important result for longer ducts where measurement of lower eigenfrequencies may present problems using standard measurement equipment. 相似文献
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Khor Soo Wei Lee Yean Kee Abas Mhd Radzi Bin Tay Kheng Soo 《Journal of Sol-Gel Science and Technology》2017,82(3):834-845
Journal of Sol-Gel Science and Technology - This study demonstrated the application of chalcone-based dithiocarbamate derivative as metal capturing ligand for the removal of mercury ion (Hg2+) in... 相似文献
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A New Megastigmane Glucoside and Three New Flavonoid Glycosides from Spiraea prunifolia var. simpliciflora 下载免费PDF全文
A new megastigmane glucoside, simplicifloranoside ( 1 ), and three new flavonol glycosides, prunifolianosides A–C ( 2 – 4 , resp.), were isolated from the aerial parts of Spiraea prunifolia var. simpliciflora. In addition, fifteen known compounds, including five phenolic acids, three lignans, four flavonoids, one eugenol glycoside, and two alkyl‐primeverosides, were also identified. Their structures were elucidated on the basis of detailed spectroscopic analyses and acid hydrolysis. 相似文献
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Kaempferol ( 1 ), a natural product from various plants, was synthesized in which the longest linear sequence is only seven steps in over all yields of 47% from commercially avail able 1,3,5‐trimethoxybenzene (10). The methylated kaempferols 2–5 were also pre pared by use of this concise synthetic methodology. The key transformations in this synthesis involved the I2 oxidative‐promoting‐cyclization and DDO oxidative hydroxylation. Several strategies to achieve 1 are provided. 相似文献
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Kim JS Yean MH Lee EJ Jung HS Lee JY Kim YJ Kang SS 《Chemical & pharmaceutical bulletin》2008,56(1):105-108
Two new cycloartane-type triterpenoid saponins were isolated from the roots of Astragalus membranaceus (FISCH.) BGE. (Leguminosae) cultivated in Kangwon province, Korea. These saponins were named astramembranosides A and B and were established to be cycloastragenol 6,25-di-O-beta-D-glucopyranoside (astramembranoside A) and cyclocanthogenin 3-O-beta-D-glucopyranosyl(1-->2)-beta-D-xylopyranoside (astramembranoside B) on the basis of chemical and spectral evidence. In addition, 12 known saponins were also isolated from the same materials. Although cycloastragenol 3-O-xyloside and agroastragalosides I and II have already been isolated from A. membranaceus adventitious roots, these three saponins together with brachyoside B and azukisaponin V methyl ester were isolated for the first time from this plant. 相似文献
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Colorectal cancer (CRC) is the fourth most common cause of death from cancer in the world. The limitations of the currently available methods and biomarkers for CRC management highlight the necessity of finding novel markers. Metabonomics can be used to search for potential markers that can provide molecular insight into human CRC. The emergence of two-dimensional gas chromatography time of flight mass spectrometry (GC?×?GC/TOFMS) has comprehensively enhanced the metabolic space coverage of conventional GC/MS. In this study, a GC?×?GC/TOFMS was developed for the tissue-based global metabonomic profiling of CRC. A Pegasus GC?×?GC/TOFMS (Leco Corp., St. Joseph, MI, USA) system comprising an Agilent 7890 GC and Pegasus IV TOFMS was used for this purpose. An Agilent DB-1 (30 m?×?250 μm?×?0.25 μm) fused silica capillary column and a Restek Rxi®-17 (1 m?×?100 μm?×?0.10 μm) fused silica capillary column were used as the primary and secondary columns, respectively. The method was applied for global metabonomic profiling of matched CRC and normal tissues (n?=?63) obtained from 31 CRC patients during surgery. An attempt was also made to compare GC?×?GC/TOFMS with GC/MS and NMR in similar application. The results showed that the metabotype associated with CRC is distinct from that of normal tissue and led to the identification of chemically diverse marker metabolites. Metabolic pathway mapping suggested deregulation of various biochemical processes such as glycolysis, Krebs cycle, osmoregulation, steroid biosynthesis, eicosanoid biosynthesis, bile acid biosynthesis, lipid, amino acid and nucleotide metabolism. 相似文献
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Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO2 was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO2 was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO2 nanotubes could be up to four times as compared to TiO2 powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO2 nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO2 nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO2 nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO2 nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes. 相似文献
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Abbasi YA Shahida S. Ali A. Khan MH Khan MI 《Journal of Radioanalytical and Nuclear Chemistry》2019,320(2):273-282
The extraction behavior of Nd(III) and Eu(III) with 0.05 mol dm−3 furosemide in benzyl alcohol as single acidic extractant and then with equimolar (0.05 mol dm−3) synergic mixture of furosemide as acidic extractant and tribenzylamine as neutral donor in benzyl alcohol has been studied from aqueous solutions of pH 1 to 6. The effect of various parameters and of various cations and anions on the extraction of these metal ions was investigated. The composition of the extracted adducts was determined by slope analysis method that came out to be [(M(FS)2)+ (CH3COO)−] and [M(FS)3·3TBA] where M = Nd(III) and Eu(III).
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