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81.
The molecular structure of tungsten oxytetrafluoride has been studied in the gas phase by electron diffraction. A square pyramidal model with molecular symmetryC4v, as indicated by vibrational spectroscopy, gives a good fit to the experimental data. Least squares refinement on the molecular intensity curves gives the following results for the principal geometrical parameters (uncertainties in parentheses are 2σ):ra(W=O) = 1.666 (0.007)Å,ra(W-F)= 1.847 (0.002)Å, ∠OWF = 104.8 (0.6)°, ∠FWF = 86.2(0.3)°. 相似文献
82.
Morten Brndvang Lise‐Lotte Gundersen 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):o274-o276
The title compound, C17H13ClN4O2, displays profound and selective activity against Mycobacterium tuberculosis. In the crystal structure, there are two independent molecules in the asymmetric unit. Intermolecular hydrogen bonding between a CH group of the purine ring and the O atom of the furan ring, and also π–π stacking in another direction, builds the three‐dimensional network. 相似文献
83.
Keinicke L Fristrup P Norrby PO Madsen R 《Journal of the American Chemical Society》2005,127(45):15756-15761
A new protocol for the synthesis of vicinal amino alcohols is described. The method employs a Barbier-type reaction between an imine and 3-benzoyloxyallyl bromide in the presence of zinc metal. The addition products are debenzoylated to afford amino alcohols in good yields and with diastereomeric ratios greater than 85:15 in favor of the anti isomer. A Hammett study has been performed which strongly indicates that the allylation does not follow a radical mechanism, but instead an organometallic reagent is formed which subsequently reacts with the imine. A computational study based on this mechanism reproduces the observed diastereoselectivity with high accuracy, but only when a sufficiently large portion of the substrate is included. 相似文献
84.
1,2,3-Triazolyl-alkylphosphonates are synthesised according to a Huisgen 1,3-dipolar cycloaddition catalysed by copper salts. The cycloaddition of either an alkynylphosphonate with an azidoalkane or an azido-phosphonate with an alkyne is achieved in high yield and regiospecifically. As an illustration of the functionalisation of aromatic ligands by using the catalytic version of the Huisgen reaction, the coupling of 3-ethynyl-1,10-phenanthroline with azidoalkylphosphonate is reported. 相似文献
85.
Nicolas Puljic Matthias Albert Anne‐Lise Dhimane Louis Fensterbank Emmanuel Lacte Max Malacria 《Helvetica chimica acta》2006,89(10):2297-2305
The titanocene(III) chloride mediated opening of silyloxiranes has been examined. Electron transfer from the metal leads to α‐silyl radicals with total regiocontrol. The radicals could be trapped by various olefins, and the corresponding adducts were obtained in good yields (Table). Further substitution of the oxirane by alkyl groups proved detrimental to the reactions, but ring opening remained essentially regioselective. 相似文献
86.
Construction of Insulin 18‐mer Nanoassemblies Driven by Coordination to Iron(II) and Zinc(II) Ions at Distinct Sites
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Dr. Henrik K. Munch Jesper Nygaard Dr. Niels Johan Christensen Dr. Christian Engelbrekt Mads Østergaard Dr. Trine Porsgaard Dr. Thomas Hoeg‐Jensen Prof. Dr. Jingdong Zhang Prof. Dr. Lise Arleth Prof. Dr. Peter W. Thulstrup Prof. Dr. Knud J. Jensen 《Angewandte Chemie (International ed. in English)》2016,55(7):2378-2381
Controlled self‐assembly (SA) of proteins offers the possibility to tune their properties or to create new materials. Herein, we present the synthesis of a modified human insulin (HI) with two distinct metal‐ion binding sites, one native, the other abiotic, enabling hierarchical SA through coordination with two different metal ions. Selective attachment of an abiotic 2,2′‐bipyridine (bipy) ligand to HI, yielding HI–bipy, enabled ZnII‐binding hexamers to SA into trimers of hexamers, [[HI–bipy]6]3, driven by octahedral coordination to a FeII ion. The structures were studied in solution by small‐angle X‐ray scattering and on surfaces with AFM. The abiotic metal ligand had a higher affinity for FeII than ZnII ions, enabling control of the hexamer formation with ZnII and the formation of trimers of hexamers with FeII ions. This precise control of protein SA to give oligomers of oligomers provides nanoscale structures with potential applications in nanomedicine. 相似文献
87.
Total Synthesis and Biological Evaluation of Rakicidin A and Discovery of a Simplified Bioactive Analogue
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Dr. Michail Tsakos Dr. Lise L. Clement Dr. Eva S. Schaffert Frank N. Olsen Sebastiano Rupiani Rasmus Djurhuus Wanwan Yu Kristian M. Jacobsen Nikolaj L. Villadsen Prof. Dr. Thomas B. Poulsen 《Angewandte Chemie (International ed. in English)》2016,55(3):1030-1035
We report a concise asymmetric synthesis of rakicidin A, a macrocyclic depsipeptide that selectively inhibits the growth of hypoxic cancer cells and stem‐like leukemia cells. Key transformations include a diastereoselective organocatalytic cross‐aldol reaction to build the polyketide portion of the molecule, a highly hindered ester fragment coupling reaction, an efficient Helquist‐type Horner—Wadsworth—Emmons (HWE) macrocyclization, and a new DSC‐mediated elimination reaction to construct the sensitive APD portion of rakicidin A. We further report the preparation of a simplified structural analogue (WY1) with dramatically enhanced hypoxia‐selective activity. 相似文献
88.
89.
Alex Cartier Etienne Levernier Vincent Corc Takahide Fukuyama Anne‐Lise Dhimane Cyril Ollivier Ilhyong Ryu Louis Fensterbank 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1803-1807
Primary, secondary, and tertiary alkyl radicals formed by the photocatalyzed oxidation of organosilicates underwent efficient carbonylation with carbon monoxide (CO) to give a variety of unsymmetrical ketones. This study introduces the possibility of radical carbonylation under a photooxidative regime. 相似文献
90.