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991.
Anna K. Renfrew Alexander E. Egger Rosario Scopelliti Christian G. Hartinger Paul J. Dyson 《Comptes Rendus Chimie》2010,13(8-9):1144-1150
Metal complexes bearing phosphine ligands are attracting increasing attention for their applications in medicinal chemistry. In particular, organometallic ruthenium-phosphine complexes have been found to exhibit promising antitumour activity. The synthesis, anticancer activity and reactivity of a novel bis-phosphine complex, [Ru(η6-cymene)(PPh2(o-C6H4O)-κ2-P,O)(pta)]Cl (pta = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1.]decane), is presented. The complex appears to exhibit its anticancer effect via a different mechanism to other ruthenium-arene pta complexes with labile co-ligands. 相似文献
992.
Daroui-Mokaddem H Kabouche A Bouacha M Soumati B El-Azzouny A Bruneau C Kabouche Z 《Natural product communications》2010,5(10):1669-1672
The essential oils of fresh leaves of Eucalyptus globulus L. (Myrtaceae), and leaves and stems of Smyrnium olusatrum L. (Apiaceae), obtained by hydrodistillation in a Clevenger-type apparatus, were analyzed by GC/MS. Twenty compounds were characterized, representing 98.3% of the essential oil of E. globulus, with 1,8-cineole (48.6%), globulol (10.9%), trans-pinocarveol (10.7%), and alpha-terpineol (6.6%) as main components, while thirty-three compounds were characterized, representing 94.3% of the essential oil of S. olusatrum, with sabinene (27.1%), curzerene (13.7%), methyl-1-benzyl-2-oxocyclooctane carboxylate (12.3%), alpha-pinene (7.2%), cryptone (7.1%) and beta-pinene (5.7%) as the major components. The essential oils of E. globulus and S. olusatrum were tested against a wide range of fungal and bacterial strains. Both oils showed significant antimicrobial activity. 相似文献
993.
Krzysztof Ejsmont Joel Boeglin Claude Didierjean Gilles Guichard Christian Jelsch 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(6):o292-o294
The crystal structure of the title compound, C16H23N3O4·CH3CN, was refined using a multipolar atom model transferred from an experimental electron‐density database. The refinement showed some improvement in crystallographic statistical indices compared with the independent atom model. The triazepane ring adopts a twist‐boat conformation. In the crystal structure, the molecule forms intermolecular contacts with 14 different neighbours. There are two N—H...O and one C—H...O intermolecular hydrogen bond. 相似文献
994.
Dr. Clelia Cogliati Dr. Laura Ragona Dr. Mariapina D'Onofrio Prof. Ulrich Günther Dr. Sara Whittaker Dr. Christian Ludwig Dr. Simona Tomaselli Dr. Michael Assfalg Prof. Henriette Molinari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(37):11300-11310
The investigation of multi‐site ligand–protein binding and multi‐step mechanisms is highly demanding. In this work, advanced NMR methodologies such as 2D 1H–15N line‐shape analysis, which allows a reliable investigation of ligand binding occurring on micro‐ to millisecond timescales, have been extended to model a two‐step binding mechanism. The molecular recognition and complex uptake mechanism of two bile salt molecules by lipid carriers is an interesting example that shows that protein dynamics has the potential to modulate the macromolecule–ligand encounter. Kinetic analysis supports a conformational selection model as the initial recognition process in which the dynamics observed in the apo form is essential for ligand uptake, leading to conformations with improved access to the binding cavity. Subsequent multi‐step events could be modelled, for several residues, with a two‐step binding mechanism. The protein in the ligand‐bound state still exhibits a conformational rearrangement that occurs on a very slow timescale, as observed for other proteins of the family. A global mechanism suggesting how bile acids access the macromolecular cavity is thus proposed. 相似文献
995.
Marc Ostermeier Dipl.‐Chem. Marie‐Anne Berlin Dipl.‐Chem. Robert M. Meudtner Dr. Serhiy Demeshko Dr. Franc Meyer Prof. Dr. Christian Limberg Prof. Dr. Stefan Hecht Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10202-10213
2,6‐Bis(1,2,3‐triazol‐4‐yl)pyridine (btp) ligands with substitution patterns ranging from strongly electron‐donating to strongly electron‐accepting groups, readily prepared by means of Cu‐catalyzed 1,3‐dipolar cycloaddition (the “click” reaction), were investigated with regard to their complexation behavior, and the properties of the resulting transition‐metal compounds were compared. Metal–btp complexes of 1:1 stoichiometry, that is, [Ru(btp)Cl2(dmso)] and [Zn(btp)Br2], could be isolated and were crystallographically characterized: they display octahedral and trigonal‐bipyramidal coordination geometries, respectively, and exhibit high aggregation tendencies due to efficient π–π stacking leading to low solubilities. Metal–btp complexes of 1:2 stoichiometry, that is, [Fe(btp)2]2+ and [Ru(btp)2]2+, could also be synthesized and their metal centers show the expected octahedral coordination spheres. The iron compounds exhibit quite a complex magnetic behavior in the solid state including spin crossover near room temperature, and hysteresis and locking into high‐spin states on tempering at 400 K, depending on the substituents on the btp ligands. Cyclic voltammetry studies of [Ru(btp)2]2+ reveal strong modulation of the oxidation potentials by more than 0.6 V and a clear linear correlation to the Hammett constant (σpara) of the substituent at the pyridine core. Isothermal titration calorimetry was used to measure the thermodynamics of the FeII–btp complexation process and enabled accurate determination of the complexation enthalpies, which display a linear relationship with the σpara values for the terminal phenyl substituents. Detailed NMR spectroscopic studies finally revealed that in the case of FeII complexation, dynamics are rapid for all investigated btp derivatives in acetonitrile, while replacing FeII by RuII or changing the solvent to dichloromethane effectively slows down ligand exchange. The results nicely demonstrate the utility of substituent parameters, originally developed for linear free‐energy relationships to explain reactivity in organic reactions, in coordination chemistry, and to illustrate the potential to custom‐design btp ligands and complexes thereof with predictable properties. The fast equilibration of the [Fe(btp)2]2+ complexes together with their tunable stability and interesting magnetic properties should enable the design of dynamic metallosupramolecular materials with advantageous properties. 相似文献
996.
Markus Stubenhofer Dipl.‐Chem. Christian Kuntz Dr. Michael Bodensteiner Dipl.‐Chem. Ulrich Zenneck Prof. Dr. Marek Sierka Dr. Manfred Scheer Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(25):7488-7495
Photolysis of [Cp*As{W(CO)5}2] ( 1 a ) in the presence of Mes*P?PMes* (Mes*=2,4,6‐tri‐tert‐butylphenyl) leads to the novel 1,3‐diphospha‐2‐arsaallyl radical [(CO)5W(μ,η2:η1‐P2AsMes*2)W(CO)4] ( 2 a ). The frontier orbitals of the radical 2 a are indicative of a stable π‐allylic system that is only marginally influenced by the d orbitals of the two tungsten atoms. The SOMO and the corresponding spin density distribution of the radical 2 a show that the unpaired electron is preferentially located at the two equivalent terminal phosphorus atoms, which has been confirmed by EPR spectroscopy. The protonated derivative of 2 a , the complex [(CO)5W(μ,η2:η1‐P2As(H)Mes*2)W(CO)4] ( 6 a ) is formed during chromatographic workup, whereas the additional products [Mes*P?PMes*{W(CO)5}] as the Z‐isomer ( 3 ) and the E‐isomer ( 4 ), and [As2{W(CO)5}3] ( 5 ) are produced as a result of a decomposition reaction of radical 2 a . Reduction of radical 2 a yields the stable anion [(CO)5W(μ,η2:η1‐P2AsMes*2)W(CO)4]? in 7 a , whereas upon oxidation the corresponding cationic complex [(CO)5W(μ,η2:η1‐P2AsMes*2)W(CO)4][SbF6] ( 8 a ) is formed, which is only stable at low temperatures in solution. Compounds 2 a , 7 a , and 8 a represent the hitherto elusive complexed redox congeners of the diphospha‐arsa‐allyl system. The analogous oxidation of the triphosphaallyl radical [(CO)5W(μ,η2:η1‐ P3Mes*2)W(CO)4] ( 2 b ) also leads to an allyl cation, which decomposes under CH activation to the phosphine derivative [(CO)5W{μ,η2:η1‐P3(Mes*)(C5H2tBu2C(CH3)2CH2)}W(CO)4] ( 9 ), in which a CH bond of a methyl group of the Mes* substituent has been activated. All new products have been characterized by NMR spectrometry and IR spectroscopy, and compounds 2 a , 3 , 6 a , 7 a , and 9 by X‐ray diffraction analysis. 相似文献
997.
Francisco López-Suevos Christian Eyholzer Nico Bordeanu Klaus Richter 《Cellulose (London, England)》2010,17(2):387-398
Suspensions of commercial refined beech pulp (RBP) were further processed through mechanical disintegration (MD-RBP), chemical
modification (CM-RBP) and through chemical modification followed by mechanical disintegration (CM-MD-RBP). Nanocomposites
were prepared by compounding a poly(vinyl acetate) (PVAc) latex adhesive with increasing contents of the different types of
nanofibrils, and the resulting nanocomposites were analyzed by dynamic mechanical analysis (DMA). Also, the suitability of
using the CM-RBP fibrils to formulate PVAc adhesives for wood bonded assemblies with improved heat resistance was studied.
The presence of cellulose nanofibrils had a strong influence on the viscoelastic properties of PVAc latex films. For all nanocomposites,
increasing amounts of cellulose nanofibrils (treated or untreated) led to increasing reinforcing effects in the glassy state,
but especially in the PVAc and PVOH glass transitions. This reinforcement primarily resulted from interactions between the
cellulose fibrils network and the hydrophilic PVOH matrix that led to the complete disappearance of the PVOH glass transition
(tan δ peak) for some fibril types and contents. At any given concentration in the PVOH transition, the CM-MD-RBP nanofibrils
provided the highest reinforcement, followed by the MD-RBP, CM-RBP and the untreated RBP. Finally, the use of the CM-RBP fibrils
to prepare PVAc reinforced adhesives for wood bonding was promising since, even though they generally performed worse in dry
and wet conditions, the boards showed superior heat resistance (EN 14257) and passed the test for durability class D1. 相似文献
998.
Semisynthetic techniques have greatly contributed to the rapid development of Chemical Biology in recent years. In this regard the semisynthesis of complex modified proteins as well as the selective derivatization of natural products has evolved into more than mere proof‐of‐principle concepts but powerful tools to probe protein functions. This technology provides a solid basis for further investigations on proteomics and qualitative and quantitative cell biology. The interdisciplinary charter bridging chemistry and biology is the hallmark of semisynthesis. It can be expected that its scientific impact will further increase in the future. 相似文献
999.
In Semisynthesis complex molecules have to be manipulated in a chemoselective, regioselective, and stereoselective fashion, necessitating smart protective group operations and innovative synthesis development. Key are always easily accessible and suitable starting materials, especially intermediates which can be produced by biotechnological processes. An extensive synthetic construction of drug candidates carries high innovative and intellectual property protection potential, hence multistep semi‐ and even total syntheses are an integral part of modern industrial research and drug development. Not a long time ago, the complexity such realized would have been inconceivable, which profoundly illustrates the progress synthesis methodology has made. Semisynthesis always aims more toward focussed application, and hence its scientific contribution mostly cater to the elucidation of molecular correlations. Especially the study of cellular processes and their quantification will be stimulated in the future. Thereby semisynthesis will continue to bridge the key future areas of synthesis research and chemical biology. 相似文献
1000.
Laura Senft Jamonica L. Moore Alicja Franke Katherine R. Fisher Andreas Scheitler Achim Zahl Ralph Puchta Dominik Fehn Sidney Ison Safaa Sader Ivana Ivanovi-Burmazovi Christian R. Goldsmith 《Chemical science》2021,12(31):10483
Reactivity assays previously suggested that two quinol-containing MRI contrast agent sensors for H2O2, [Mn(H2qp1)(MeCN)]2+ and [Mn(H4qp2)Br2], could also catalytically degrade superoxide. Subsequently, [Zn(H2qp1)(OTf)]+ was found to use the redox activity of the H2qp1 ligand to catalyze the conversion of O2˙− to O2 and H2O2, raising the possibility that the organic ligand, rather than the metal, could serve as the redox partner for O2˙− in the manganese chemistry. Here, we use stopped-flow kinetics and cryospray-ionization mass spectrometry (CSI-MS) analysis of the direct reactions between the manganese-containing contrast agents and O2˙− to confirm the activity and elucidate the catalytic mechanism. The obtained data are consistent with the operation of multiple parallel catalytic cycles, with both the quinol groups and manganese cycling through different oxidation states during the reactions with superoxide. The choice of ligand impacts the overall charges of the intermediates and allows us to visualize complementary sets of intermediates within the catalytic cycles using CSI-MS. With the diquinolic H4qp2, we detect Mn(iii)-superoxo intermediates with both reduced and oxidized forms of the ligand, a Mn(iii)-hydroperoxo compound, and what is formally a Mn(iv)-oxo species with the monoquinolate/mono-para-quinone form of H4qp2. With the monoquinolic H2qp1, we observe a Mn(ii)-superoxo ↔ Mn(iii)-peroxo intermediate with the oxidized para-quinone form of the ligand. The observation of these species suggests inner-sphere mechanisms for O2˙− oxidation and reduction that include both the ligand and manganese as redox partners. The higher positive charges of the complexes with the reduced and oxidized forms of H2qp1 compared to those with related forms of H4qp2 result in higher catalytic activity (kcat ∼ 108 M−1 s−1 at pH 7.4) that rivals those of the most active superoxide dismutase (SOD) mimics. The manganese complex with H2qp1 is markedly more stable in water than other highly active non-porphyrin-based and even some Mn(ii) porphyrin-based SOD mimics.Manganese complexes with polydentate quinol-containing ligands are found to catalyze the degradation of superoxide through inner-sphere mechanisms. The redox activity of the ligand stabilizes higher-valent manganese species. 相似文献