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71.
A new lignan glycoside, 1,5-dihydroxy-2-(4"-beta-D-glucopyranosyloxy-3"-methoxyphenyl)-6-(4'-hydroxy-3'-methoxyphenyl)-3,7-dioxabicyclo[3.3.0]octane, named ambrosidine ([structure: see text]), along with seven known compounds (four iridoids and three hydroxycinnamic esters) were isolated from the roots of Cephalaria ambrosioides. The structures of these compounds were determined by use of NMR and MS techniques and by chemical transformations. The cytotoxic activity of the novel compound [structure: see text] was evaluated against five human solid tumour cell lines. 相似文献
72.
Insights into the Catalytic Activity of Nitridated Fibrous Silica (KCC‐1) Nanocatalysts from 15N and 29Si NMR Spectroscopy Enhanced by Dynamic Nuclear Polarization 下载免费PDF全文
Dr. Aany Sofia Lilly Thankamony Dr. Cédric Lion Dr. Frédérique Pourpoint Baljeet Singh Dr. Angel J. Perez Linde Dr. Diego Carnevale Prof. Geoffrey Bodenhausen Dr. Hervé Vezin Prof. Olivier Lafon Prof. Vivek Polshettiwar 《Angewandte Chemie (International ed. in English)》2015,54(7):2190-2193
Fibrous nanosilica (KCC‐1) oxynitrides are promising solid‐base catalysts. Paradoxically, when their nitrogen content increases, their catalytic activity decreases. This counterintuitive observation is explained here for the first time using 15N‐solid‐state NMR spectroscopy enhanced by dynamic nuclear polarization. 相似文献
73.
Metal‐Doped Nitrogenated Carbon as an Efficient Catalyst for Direct CO2 Electroreduction to CO and Hydrocarbons 下载免费PDF全文
Dr. Ana Sofia Varela Dr. Nastaran Ranjbar Sahraie Julian Steinberg Wen Ju Dr. Hyung‐Suk Oh Prof. Dr. Peter Strasser 《Angewandte Chemie (International ed. in English)》2015,54(37):10758-10762
This study explores the kinetics, mechanism, and active sites of the CO2 electroreduction reaction (CO2RR) to syngas and hydrocarbons on a class of functionalized solid carbon‐based catalysts. Commercial carbon blacks were functionalized with nitrogen and Fe and/or Mn ions using pyrolysis and acid leaching. The resulting solid powder catalysts were found to be active and highly CO selective electrocatalysts in the electroreduction of CO2 to CO/H2 mixtures outperforming a low‐area polycrystalline gold benchmark. Unspecific with respect to the nature of the metal, CO production is believed to occur on nitrogen functionalities in competition with hydrogen evolution. Evidence is provided that sufficiently strong interaction between CO and the metal enables the protonation of CO and the formation of hydrocarbons. Our results highlight a promising new class of low‐cost, abundant electrocatalysts for synthetic fuel production from CO2. 相似文献
74.
The influence of various reclamation agents (montmorillonite, peat, activated sludge microbocenosis) on the stability of dispersions of the colloidal fraction of meadow chernozem soil is studied. It is established that biocolloids possess the strongest coagulating action in the aforementioned series of reclamation agents. It is shown that, in the process of microorganism growth involving glucose or polypeptides as a carbon source, exopolymers are synthesized that caused the coagulation of soil dispersions. Upon the growth of microorganisms on polypeptides (alkaligeneous metabolism), precipitates are formed that are denser and less peptized by water than those grown on glucose (acidogeneous metabolism). The addition of montmorillonite and peat intensifies the aggregation processes in soil-microbe heterodispersions. The inverse relationship between the content of an organic substance in a colloidal system and the stability of aggregates of soil colloids is revealed. 相似文献
75.
Matthias Roßberg Werner Strube Jrg Wollbrandt Eberhard Linke 《Journal of photochemistry and photobiology. A, Chemistry》1994,80(1-3):61-65
In this paper, we investigate the rotationally resolved spectra of hot CF radicals generated after IR multiphoton dissociation (IRMPD) of CFCl3 or CF2Cl2 and subsequent UV photodissociation. It is shown that these conditions are advantageous for the spectroscopy of transitions involving high rotational quantum numbers and hot bands. Thus molecular constants of CF for the first vibrationally excited state of the electronic ground state (Av=77.1 cm−1, Bv=1.389 cm−1, Dv=6.570×10−6 cm−1) are determined for the first time or are calculated more accurately. The spectroscopic method used was resonance-enhanced multiphoton ionization (REMPI) spectroscopy. 相似文献
76.
Reddy PG Chun BK Zhang HR Rachakonda S Ross BS Sofia MJ 《The Journal of organic chemistry》2011,76(10):3782-3790
PSI-352938 is a novel 2'-deoxy-2'-α-fluoro-2'-β-C-methyl 3',5'-cyclic phosphate nucleotide prodrug currently under investigation for the treatment of hepatitis C virus (HCV) infection. PSI-352938 demonstrated superior characteristics in vitro that include broad genotype coverage, superior resistance profile, and high levels of active triphosphate in vivo in the liver compared to our first and second generation nucleoside inhibitors of this class. Consequently, PSI-352938 was selected for further development and an efficient and scalable synthesis was sought to support clinical development. We report an improved, diastereoselective synthesis of a key 1'-β-nucleoside intermediate 13 via S(N)2 displacement of 1-α-bromo ribofuranose sugar 16 with the potassium salt of 6-chloro-2-amino purine and an efficient method to prepare cis-Rp cyclic phosphate (PSI-352938) in a highly stereoselective manner without any chromatographic purification. The 1-α-bromo sugar 16 was stereospecifically prepared from the corresponding 1-β-lactol in high yield under mild bromination conditions using CBr(4)/PPh(3) (Appel reaction). The desired cis-Rp 3',5'-cyclic phosphate construction was accomplished using isopropyl phosphorodichloridate readily obtained from POCl(3) and isopropyl alcohol. The base combination of Et(3)N/NMI was identified as a key factor for producing PSI-352938 as the major (>95%) diastereomer (cis-Rp) in high yield after the final cyclization step. The current route described in this article was successfully used to produce PSI-352938 on multikilogram scale. 相似文献
77.
Rimantas Vaitkus Stefan Sj?berg 《Journal of inclusion phenomena and macrocyclic chemistry》2011,69(3-4):393-395
Complexation of some o-, m- and p-carborane derivatives with ??-cyclodextrin was investigated using phenolphthalein in pH 10.5 (0.05 mol dm?3) borate buffer. Some carborane derivatives indicated large inclusion constants Kass > 1 × 105 dm3 mol?1. 相似文献
78.
Ciobanu M Huang KT Daguer JP Barluenga S Chaloin O Schaeffer E Mueller CG Mitchell DA Winssinger N 《Chemical communications (Cambridge, England)》2011,47(33):9321-9323
We report the synthesis of a nucleic acid-encoded carbohydrate library, its combinatorial self-assembly into 37,485 pairs and a screen against DC-SIGN leading to the identification of consensus ligand motifs. A prototypical example from the selected pairs was shown to have enhanced binding. A dendrimer incorporating the selected motifs inhibited gp120's binding to dendritic cells with higher efficiency than mannan. 相似文献
79.
Dembski S Milde M Dyrba M Schweizer S Gellermann C Klockenbring T 《Langmuir : the ACS journal of surfaces and colloids》2011,27(23):14025-14032
A novel method for the synthesis of luminescent SiO(2)/calcium phosphate (CaP):Eu(3+) core-shell nanoparticles (NPs) was developed via a sol-gel route followed by annealing at a temperature of 800 °C. The object of this study was the investigation of the effect of pH on the formation of a CaP shell around the silica core. The resulting annealed NPs exhibited an amorphous SiO(2) core and a crystalline luminescent shell. The formation of a CaP layer was possible at pH below 4.5 and above 6.5 during the coating step. The crystal structure of the shell was studied by X-ray diffraction analysis. Hydroxyapatite (HAp) and α-tricalcium phosphate were detected as crystal phases of the surrounding layer. However, NPs produced under basic conditions exhibited a higher crystallinity of the CaP layer than did samples coated at pH below 4.5. In the pH interval between 4.5 and 6.5, no shell growth but the formation of secondary NPs containing CaO and Ca(OH)(2) was observed. Furthermore, SiO(2)/CP:Eu(3+) core-shell NPs were investigated by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectrometry, and photoluminescence spectroscopy. The resulting HAp-coated NPs were successfully tested by a cell-culture-based viability assay with respect to a later application as a luminescent marker for biomedical applications. 相似文献
80.
Sofia Nikolaou Sérgio Hiroshi Toma Vagner Roberto de Souza Juliano B. Alves Koiti Araki Henrique Eisi Toma 《Transition Metal Chemistry》2011,36(7):775-783
The triruthenium carboxylate cluster [Ru3O(OAc)6(py)2(bpp)]+ (OAc = acetate) containing the bridging 1,3-bis(4-pyridyl)propane (bpp) ligand, and its dimeric species [{Ru3O(OAc)6(py2)}2(μ-bpp)]2+ were synthesized in order to investigate their inclusion compounds with β-cyclodextrin (β-CD). Characterization of the complexes
was carried out based on spectroscopic, electrochemical and spectroelectrochemical techniques, while the formation of inclusion
complexes was evaluated using 1H NMR/NOESY spectroscopy. Since bpp is a flexible ligand, a DFT study was carried out in order to characterize its conformational
isomers and their possible role in the host–guest chemistry with β-CD. Instead of observing the formation of inclusion compounds
with different stoichiometries, we observed the formation of 1:1 bpp/β-CD compounds in which the bpp ligand assumes different
conformations. The assembly of polymetallic rotaxane species was successfully demonstrated by monitoring the 1H NMR spectra of the monomeric cluster species in the presence of aquapentacyanoferrate(II) ions and β-CD. 相似文献