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821.
822.
Gedrich K Heitbaum M Notzon A Senkovska I Fröhlich R Getzschmann J Mueller U Glorius F Kaskel S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(7):2099-2106
Chiral metal–organic frameworks with a three‐dimensional network structure and wide‐open pores (>30 Å) were obtained by using chiral trifunctional linkers and multinuclear zinc clusters. The linkers, H3ChirBTB‐n, consist of a 4,4′,4′′‐benzene‐1,3,5‐triyltribenzoate (BTB) backbone decorated with chiral oxazolidinone substituents. The size and polarity of these substituents determines the network topology formed under solvothermal synthesis conditions. The resulting chiral MOFs adsorb even large molecules from solution. Moreover, they are highly active Lewis acid catalysts in the Mukaiyama aldol reaction. Due to their chiral functionalization, they show significant levels of enantioselectivity, thereby proving the validity of the modular design concept employed. 相似文献
823.
Hitzfeld KL Gehre M Richnow HH 《Rapid communications in mass spectrometry : RCM》2011,25(20):3114-3122
A novel approach for the measurement of (37)Cl, (81)Br and (34)S in organic compounds containing chlorine, bromine, and sulphur is presented to overcome some of the major drawbacks of existing methods. Contemporary methods either require reference materials with the exact molecular compositions of the substances to be tested, or necessitate several laborious offline procedures prior to isotope analysis. In our online setup, organic compounds are separated by gas chromatography (GC) coupled to a high-temperature reactor. Using hydrogen as a makeup gas, the reactor achieves quantitative conversion of chlorinated, brominated and sulphurated organic compounds into gaseous hydrogen chloride (HCl), hydrogen bromide (HBr), and hydrogen sulphide (H(2)S), respectively. In this study, the GC interface was coupled to a quadrupole mass spectrometer operated in single-ion mode. The ion traces of either H(35)Cl (m/z 36) and H(37)Cl (m/z 38), H(79)Br (m/z 80) and H(81)Br (m/z 82), or H(2)(32)S (m/z 34) and H(2)(34)S (m/z 36), were recorded to determine the isotopic ratios of chlorine, bromine, and sulphur isotopes. The conversion interface presented here provides a basis for a novel method for compound-specific isotope analysis of halogenated and sulphur-containing compounds. Rapid online measurements of organic chlorine-, bromine- and sulphur-containing mixtures will facilitate the isotopic analysis of compounds containing these elements, and broaden their usage in fields of environmental forensics employing isotopic concepts. 相似文献
824.
An approximate mean field model of an ensemble of delayed coupled stochastic Hindmarsh-Rose bursting neurons is constructed and analyzed. Bifurcation analysis of the approximate system is performed using numerical continuation. It is demonstrated that the stability domains in the parameter space of the large exact systems are correctly estimated using the much simpler approximate model. 相似文献
825.
Andrew W. Stevenson Sheridan C. Mayo Daniel H?usermann Anton Maksimenko Richard F. Garrett Christopher J. Hall Stephen W. Wilkins Robert A. Lewis Damian E. Myers 《Journal of synchrotron radiation》2010,17(1):75-80
The Imaging and Medical beamline at the Australian Synchrotron achieved `first light' in December 2008. Here, the first experiments performed on the beamline are reported, which involved both X‐ray imaging and tomography studies for a range of samples. The use of a plastic‐edge phantom for quantitative measurements of contrast and resolution proved to be very instructive and helped to confirm certain parameter values such as the effective horizontal source size, detector resolution and average X‐ray energy for the polychromatic beam. 相似文献
826.
Mikhail V. Kalyaev Dmitry S. Ryabukhin Marina A. Borisova Alexander Yu. Ivanov Irina A. Boyarskaya Kristina E. Borovkova Lia R. Nikiforova Julia V. Salmova Nikolay V. Ulyanovskii Dmitry S. Kosyakov Aleksander V. Vasilyev 《Molecules (Basel, Switzerland)》2022,27(14)
Reactions of 3-(furan-2-yl)propenoic acids and their esters with arenes in Brønsted superacid TfOH affords products of hydroarylation of the carbon–carbon double bond, 3-aryl-3-(furan-2-yl)propenoic acid derivatives. According to NMR and DFT studies, the corresponding O,C-diprotonated forms of the starting furan acids and esters should be reactive electrophilic species in these transformations. Starting compounds and their hydroarylation products, at a concentration of 64 µg/mL, demonstrate good antimicrobial activity against yeast-like fungi Candida albicans. Apart from that, these compounds suppress Escherichia coli and Staphylococcus aureus. 相似文献
827.
828.
Well defined all-acrylic graft copolymers have been synthesized using the macromonomer technique. Poly(methyl methacrylate) (PMMA) macromonomers of controlled molecular weight and narrow molecular weight distribution have been synthesized by group transfer polymerization (GTP) using a protected hydroxyl functional initiator. These macromonomers were quantitatively functionalized with a polymerizable acrylic and group and copolymerized under free radical conditions with 2-ethylhexyl acrylate (2EHA) to form the desired well defined graft copolymers in high yields. The macromonomers and the copolymers have been characterized by a variety of spectroscopic, chromatographic and thermal analysis methods. Transparent, multiphase materials with glass transition temperature (Tg) values of approximately -65 °C and 115 °C were obtained. The reaction conditions necessary to generate these materials most effectively have also been investigated and are described herein. 相似文献
829.
New amidino‐benzimidazolyl‐substituted bis‐1,2‐(2‐thienyl)ethenes ( 4, 5 , and 6 ) and benzo[1,2‐ b:4,3‐ b′]dithiophenes ( 8, 9 , and 10 ) were prepared by the condensation of amidino‐substituted o‐phenylene diamines with corresponding dialdehydes ( 3 and 7 ). All prepared amidino‐benzimidazolyl‐substituted compounds are of particular interest, because they can serve as intercalators or groove binders on DNA in anticancer therapy. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:218–222, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10126 相似文献
830.
Frank Würthner Stefan Brse Norbert Sewald Rainer Herges Matthias O. Senge Thorsten Bach Thomas Gottwald Thomas Kopf Kristina pehar Jens Hartung Dietmar Plattner Andreas Gansuer Martin Oestreich Reinhard Brückner Jrg Pietruszka Roderick Süßmuth Michael Müller Elmar Weinhold Andres Jschke Markus Albrecht Henning Priepke Gerhard Roth Klaus Ditrich Alexander Ernst Lars Wortmann Schering Ag 《Nachrichten aus der Chemie》2003,51(3):286-315
Die enantioselektive Synthese bleibt zentrales Thema in metallorganischen, metallfreien and bioorganischen Transformationen sowie in der industriellen organischen Chemie. Glanzpunkte zielmolekülorientierter Synthesechemie waren ein Zugang zu C60, die Route zum Diazonamid A und die Totalsynthese von Vinblastin. Mit „Pyrrolysin”︁ wurde die 22. proteinogene Aminosäure entdeckt. Trotz der immer höheren Zahl an Testsubstanzen besteht in der medizinischen Chemie ein Engpass an klinisch erfolgreichen Wirkstoffen. 相似文献