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61.
Brice JL Harang JE Timokhin VI Anastasi NR Stahl SS 《Journal of the American Chemical Society》2005,127(9):2868-2869
The first examples of palladium-catalyzed oxidative amination of unactivated alkyl olefins have been identified. To be successful, these reactions must be conducted under cocatalyst-free conditions that involve direct dioxygen-coupled turnover of the palladium catalyst. The oxidative amination products of norbornene and other cyclic alkenes implicate a cis-aminopalladation mechanism. 相似文献
62.
Toxic Dopamine Metabolite DOPAL Forms an Unexpected Dicatechol Pyrrole Adduct with Lysines of α‐Synuclein
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Dr. Jon W. Werner‐Allen Dr. Jenna F. DuMond Dr. Rodney L. Levine Dr. Ad Bax 《Angewandte Chemie (International ed. in English)》2016,55(26):7374-7378
Parkinson's disease has long been known to involve the loss of dopaminergic neurons in the substantia nigra and the coincidental appearance of Lewy bodies containing oligomerized forms of α‐synuclein. The “catecholaldehyde hypothesis” posits a causal link between these two central pathologies mediated by 3,4‐dihydroxyphenylacetaldehyde (DOPAL), the most toxic dopamine metabolite. Here we determine the structure of the dominant product in reactions between DOPAL and α‐synuclein, a dicatechol pyrrole lysine adduct. This novel modification results from the addition of two DOPAL molecules to the Lys sidechain amine through their aldehyde moieties and the formation of a new carbon–carbon bond between their alkyl chains to generate a pyrrole ring. The product is detectable at low concentrations of DOPAL and its discovery should provide a valuable chemical basis for future studies of DOPAL‐induced crosslinking of α‐synuclein. 相似文献
63.
Adam J. Zoll Jenna C. Molas Brandon Q. Mercado Prof. Jonathan A. Ellman 《Angewandte Chemie (International ed. in English)》2023,62(1):e202210822
A multicomponent annulation that proceeds by imine directed Cp*RhIII-catalyzed N−H functionalization is disclosed. The transformation affords piperazinones displaying a range of functionality and is the first example of transition metal-catalyzed multicomponent N−H functionalization. A broad range of readily available α-amino amides, including those derived from glycine, α-substituted, and α,α-disubstituted amino acids, were effective inputs and enabled the incorporation of a variety of amino acid side chains with minimal racemization. Branched and unbranched alkyl aldehydes and various stabilized diazo compounds were also efficient reactants. The piperazinone products were further modified through efficient transformations. Mechanistic studies, including X-ray crystallographic characterization of a catalytically competent five-membered rhodacycle with imine and amide nitrogen chelation, provide support for the proposed mechanism. 相似文献
64.
Adam J. Zoll Jenna C. Molas Brandon Q. Mercado Prof. Jonathan A. Ellman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202210822
A multicomponent annulation that proceeds by imine directed Cp*RhIII-catalyzed N−H functionalization is disclosed. The transformation affords piperazinones displaying a range of functionality and is the first example of transition metal-catalyzed multicomponent N−H functionalization. A broad range of readily available α-amino amides, including those derived from glycine, α-substituted, and α,α-disubstituted amino acids, were effective inputs and enabled the incorporation of a variety of amino acid side chains with minimal racemization. Branched and unbranched alkyl aldehydes and various stabilized diazo compounds were also efficient reactants. The piperazinone products were further modified through efficient transformations. Mechanistic studies, including X-ray crystallographic characterization of a catalytically competent five-membered rhodacycle with imine and amide nitrogen chelation, provide support for the proposed mechanism. 相似文献
65.
66.
Instead of reacting via the expected coarctate cyclization pathway, 2-nitrosobenzonitrile undergoes a tandem nitroso-ene/intramolecular cyclization to form benzo[c]isoxazol-3(1H)-imines in very good yields under neutral conditions and at moderate temperatures. Treatment of three of the imines with HBF4 results in dimerization/condensation to furnish unusual, delocalized cationic systems. 相似文献
67.
Tunable Crystallinity and Charge Transfer in Two‐Dimensional G‐Quadruplex Organic Frameworks
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Prof. Yi‐Lin Wu Dr. N. Scott Bobbitt Jenna L. Logsdon Natalia E. Powers‐Riggs Jordan N. Nelson Xiaolong Liu Timothy C. Wang Prof. Randall Q. Snurr Prof. Joseph T. Hupp Prof. Omar K. Farha Prof. Mark C. Hersam Prof. Michael R. Wasielewski 《Angewandte Chemie (International ed. in English)》2018,57(15):3985-3989
DNA G‐quadruplex structures were recently discovered to provide reliable scaffolding for two‐dimensional organic frameworks due to the strong hydrogen‐bonding ability of guanine. Herein, 2,7‐diaryl pyrene building blocks with high HOMO energies and large optical gaps are incorporated into G‐quadruplex organic frameworks. The adjustable substitution on the aryl groups provides an opportunity to elucidate the framework formation mechanism; molecular non‐planarity is found to be beneficial for restricting interlayer slippage, and the framework crystallinity is highest when intermolecular interaction and non‐planarity strike a fine balance. When guanine‐functionalized pyrenes are co‐crystallized with naphthalene diimide, charge‐transfer (CT) complexes are obtained. The photophysical properties of the pyrene‐only and CT frameworks are characterized by UV/Vis and steady‐state and time‐resolved photoluminescence spectroscopies, and by EPR spectroscopy for the CT complex frameworks. 相似文献
68.
Evan M. White Jeremy Yatvin Joe B. Grubbs III Jenna A. Bilbrey Jason Locklin 《Journal of polymer science. Part A, Polymer chemistry》2013,51(14):1084-1099
This review highlights recent developments in the field of stimuli-responsive hydrogels, focusing primarily on thin films, with a thickness range between 100 nm to 10 μm. The theory and dynamics of hydrogel swelling is reviewed, followed by specific applications. Gels are classified based on the active stimulus—mechanical, chemical, pH, heat, and light—and fabrication methods, design constraints, and novel stimuli-responses are discussed. Often, these materials display large physiochemical reactions to a relatively small stimulus. Noteworthy materials larger than 10 μm, but with response times on the order of seconds to minutes are also discussed. Hydrogels have the potential to advance the fields of medicine and polymer science as useful substrates for “smart” devices. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1084–1099 相似文献
69.
70.
Kepczynski M Jamróz D Wytrwal M Bednar J Rzad E Nowakowska M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(1):676-688
The interactions between synthetic polycations and phospholipid bilayers play an important role in some biophysical applications such as gene delivery or antibacterial usage. Despite extensive investigation into the nature of these interactions, their physical and molecular bases remain poorly understood. In this Article, we present the results of our studies on the impact of a hydrophobically modified strong polycation on the properties of a zwitterionic bilayer used as a model of the mammalian cellular membrane. The study was carried out using a set of complementary experimental methods and molecular dynamic (MD) simulations. A new polycation, poly(allyl-N,N-dimethyl-N-hexylammonium chloride) (polymer 3), was synthesized, and its interactions with liposomes composed of 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC) were examined using dynamic light scattering (DLS), zeta potential measurements, and cryo-transmission electron microscopy (cryo-TEM). Our results have shown that polymer 3 can efficiently associate with and insert into the POPC membrane. However, it does not change its lamellar structure, as was demonstrated by cryo-TEM. The influence of polymer 3 on the membrane functionality was studied by leakage experiments applying a fluorescence dye (calcein) encapsulated in the phospholipid vesicles. The MD simulations of model systems reveal that polymer 3 promotes formation of hydrophilic pores in the membrane, thus increasing considerably its permeability. 相似文献