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排序方式: 共有558条查询结果,搜索用时 15 毫秒
91.
92.
Marie-Ange Lespinasse Dr. Kaiyao Wei Justine Perrin Dr. Matthias Winkler Sieme Hamaidia Alexis Leroy Dr. Zuzana Macek Jilkova Dr. Christian Philouze Dr. Patrice N. Marche Dr. Carlo Petosa Dr. Jérôme Govin Dr. Anouk Emadali Dr. Yung-Sing Wong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(64):e202202293
The pharmaceutical industry has a pervasive need for chiral specific molecules with optimal affinity for their biological targets. However, the mass production of such compounds is currently limited by conventional chemical routes, that are costly and have an environmental impact. Here, we propose an easy access to obtain new tetrahydroquinolines, a motif found in many bioactive compounds, that is rapid and cost effective. Starting from simple raw materials, the procedure uses a proline-catalyzed Mannich reaction followed by the addition of BF3 ⋅ OEt2, which generates a highly electrophilic aza-ortho-quinone methide intermediate capable of reacting with different nucleophiles to form the diversely functionalized tetrahydroquinoline. Moreover, this enantioselective one-pot process provides access for the first time to tetrahydroquinolines with a cis-2,3 and trans-3,4 configuration. As proof of concept, we demonstrate that a three-step reaction sequence, from simple and inexpensive starting compounds and catalysts, can generate a BD2-selective BET bromodomain inhibitor with anti-inflammatory effect. 相似文献
93.
94.
Interfacial Nanoprecipitation toward Stable and Responsive Microbubbles and Their Use as a Resuscitative Fluid 下载免费PDF全文
Dr. Yifeng Peng Dr. Raymond P. Seekell Alexis R. Cole Jemima R. Lamothe Andrew T. Lock Sarah van den Bosch Xiaoqi Tang Prof. Dr. John N. Kheir Prof. Dr. Brian D. Polizzotti 《Angewandte Chemie (International ed. in English)》2018,57(5):1271-1276
A new approach has been developed to prepare stable microbubbles (MBs) by interfacial nanoprecipitation of bioabsorbable polymers at air/liquid interfaces. This facile method offers robust control over the morphology and chemophysical properties of MBs by simple chemical modifications. This approach is amenable to large‐scale manufacturing, and is useful to develop functional MBs for advanced biomedical applications. To demonstrate this, a MB‐based intravenous oxygen carrier was created that undergoes pH‐triggered self‐elimination. Intravenous injection of previous MBs increased the risk of pulmonary vascular obstruction. However, we show, for the first time, that our current design is superior, as they 1) yielded no evidence of acute risks in rodents, and 2) improved the survival in a disease model of asphyxial cardiac arrest (from 0 to 100 %), a condition that affects more than 100 000 in‐hospital patients, and carries a mortality of about 90 %. 相似文献
95.
Lubin-Germain N Baltaze JP Coste A Hallonet A Lauréano H Legrave G Uziel J Augé J 《Organic letters》2008,10(5):725-728
Indium-mediated alkynylation reaction was studied for the direct preparation of C-glycosides. Easily available starting sugar derivatives with an acetyl group at the anomeric position were tested as electrophiles toward alkynylindium reagents under Barbier conditions. Good yields and stereoselectivities were observed during the reaction. The alkynylation was applied to the synthesis of an alpha-(1-->6)-C-disaccharide analogue of isomaltoside. 相似文献
96.
Bueno C Mikelsons L Maretti L Scaiano JC Aspée A 《Photochemistry and photobiology》2008,84(6):1535-1542
The photophysical properties of the nitroxide prefluorescent probes 4-(3-hydroxy-2-methyl-4-quinolinoyloxy)-2,2,6,6-tetramethyl-piperidin-4-yl) ester free radical (QT) and 2,3,4,6,7,8-hexahydro-quinolizino [1,10,9-gh] coumarin-3-carboxylic acid (1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yl) ester free radical (C343T) were evaluated as a function of pH and solvent properties. The absorbance of QT showed high pH sensitivity. The pKa values for the different ionization forms involved in the acid-base equilibrium of the quinoline chromophore were determined in the ground and excited states. The fluorescence lifetimes of QT, and N-hydroxylamine (QTH) and quinoline methyl ester (QMe) derivatives, showed that the intramolecular quenching efficiency by the nitroxide moiety is independent of the quinoline ionization form. The fluorescence and absorbance of C343T were highly sensitive to solvent polarity in agreement with a charged transfer excited state of the chromophore. However, we noted a decrease in the intramolecular fluorescence quenching efficiency by the nitroxide moiety when changing the polarity of the solvent from hexane to water. This behavior has been attributed to a suppression of an energy transfer mechanism in the nitroxide quenching process in very polar solvents. The results obtained in micelles allow us to propose QT and C343T as sensors for pH and micropolarity, respectively, in addition to their role as monitors for free radicals or hydrogen transfer from phenols. 相似文献
97.
Dr. Alexis Bordet Prof. Dr. Walter Leitner 《Angewandte Chemie (International ed. in English)》2023,62(33):e202301956
The rapidly growing importance of green hydrogen and renewable carbon resources as essential feedstocks for sustainable chemical value chains opens room for disruptive innovations regarding chemical production processes. The fluctuation and variability associated with non-fossil energy and raw material supply holds many challenges for catalysts to cope with the resulting dynamics. However, many new opportunities also arise once catalyst design starts to aim at performance that is “adaptive” rather than “task-specific”. In this Scientific Perspective, we propose to define adaptivity in catalysis on the basis of three essential properties that are reversibility, rapidity, and robustness (R3 rule). Promising design strategies and selected examples are described to substantiate the scientific concept and to highlight its potential for chemical energy conversion. 相似文献
98.
We investigated the impact of calcium and magnesium ions on the deposition kinetics of flagellated and nonflagellated Pseudomonas aeruginosa onto an alginate conditioning film in a radial stagnation point flow system. The bacterial deposition/adhesion behavior was related to structural changes of the alginate film in the presence of the divalent cations. Our results showed that adhesion of nonmotile bacteria was governed by cation bridging interactions between high-affinity sites at the bacterial surface and either clean or alginate-conditioned substrate surfaces. For motile bacteria, the adhesion onto clean quartz was governed by electrostatic interactions while adhesion onto alginate-conditioned quartz was dependent on the structure and viscoelastic properties of the alginate film in the presence of calcium or magnesium. We demonstrate that bacterial adhesion behavior is governed both by the effects of divalent cations on the surface properties of the bacteria and the substrate and by the type of specific interactions occurring between these two surfaces. 相似文献
99.
Irene Zacharaki Christos Kontoyannis Alexis Lycourghiotis Christos Kordulis 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,324(1-3):208-216
Mesoporous anatase was prepared following sol–gel and using urea as template. The influence of calcination temperature on the phase stability, nanocrystal/aggregate size, pore size distribution and specific surface area as well as on the acid–base behavior in aqueous solutions was studied using X-ray diffraction, laser-Raman and diffuse reflectance spectroscopies, scanning electron microscopy and laser scattering as well as N2 adsorption–desorption isotherms and potentiometric mass titrations.The crystal structure was kept constant upon calcination over the whole temperature range, 200–500 °C. In this range anatase is constituted from primary nanocrystals. These are assembled into larger, rather spherical, clusters of about 30–40 nm and then into aggregates of various sizes (0.2–0.3 μm and 2–100 μm) with a distribution centered at about 12 μm. Increase of the calcination temperature caused an increase in the size of the primary nanocrystals from 8.1 nm at 200 °C to 17.1 nm at 500 °C, whereas calcination does not influence the morphology at micro-scale. Moreover, increase of the calcination temperature from 200 °C to 500 °C brings about a shift in the mean pore diameter from 47 nm to 91 nm accompanied by a decrease in the specific surface area and pore volume. The above effects were related with the aforementioned increase in the size of the primary nanocrystals. The value of pzc and the values of surface charge determined at various pH do not practically depend on the calcination temperature. The absence of pore space confinement effects was explained in terms of the structure and size of the interface development between the anatase surface and the electrolytic solution. 相似文献
100.
Alexis Morales Jochem Struppe Enrique Meléndez 《Journal of inclusion phenomena and macrocyclic chemistry》2008,60(3-4):263-270
The possible inclusion complexes of Cp2NbCl2 into α-, β-, and γ-CD hosts have been investigated. The existence of a true inclusion complex in the solid state was confirmed
by a combination of thermogravimetric analysis, FTIR, PXRD, and 13C CP-MAS NMR spectroscopies. The solid-state results demonstrated that α-cyclodextrin does not form inclusion complexes with
Cp2NbCl2 whereas β- and γ-cyclodextrins do form such complexes. PXRD, NMR, and thermal analysis showed that the organometallic molecules
of Cp2NbCl2OH are included in the cavities of β- and γ-cyclodextrins, possibly adopting a symmetrical conformation in the complex, with
each glucose unit in a similar environment. In solution, 1H NMR experiments suggest that niobocene has a shallow penetration on the β-CD leading to upfield shift on H-3 signal with
a minor perturbation on the H-5 proton while for γ-CD, both H-3 and H-5 are shifted upfield substantially. This suggests that
niobocene penetrates deeper into the γ-CD cavity than in the β-CD cavity, as a result of the cavity size.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献