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Michael Heinz Gregor Weiss Dr. Grigoriy Shizgal Dr. Anastasia Panfilova Prof. Dr. Andreas Gansäuer 《Angewandte Chemie (International ed. in English)》2023,62(38):e202308680
We describe a unique catalytic system with an efficient coupling of Ti- and Cr-catalysis in a reaction network that allows the use of [BH4]− as stoichiometric hydrogen atom and electron donor in catalytic radical chemistry. The key feature is a relay hydrogen atom transfer from [BH4]− to Cr generating the active catalysts under mild conditions. This enables epoxide reductions, regiodivergent epoxide opening and radical cyclizations that are not possible with cooperative catalysis with radicals or by epoxide reductions via Meinwald rearrangement and ensuing carbonyl reduction. No typical SN2-type reactivity of [BH4]− salts is observed. 相似文献
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Franziska Hausig-Punke Gregor Dekevic Fabian H. Sobotta Jana I. Solomun Friederike Richter Denise Salzig Anja Traeger Johannes C. Brendel 《Macromolecular bioscience》2023,23(5):2370016
Cationic pH-responsive polymers promise to overcome critical challenges in cellular delivery. Ideally, the polymers become selectively charged along the endosomal pathway disturbing only the local membrane and avoiding unintended interactions or cytotoxic side effects at physiological conditions. Polypiperazines represent a novel, hydrophilic class of pH-responsive polymers whose response can be tuned within the relevant pH range (5–7.4). The authors discovered that the polypiperazines are effectively binding plasmid DNA (pDNA) and demonstrate high efficiency in transfection. By design of experiments (DoE), a wide parameter space (pDNA and polymer concentration) is screened to identify the range of effective concentrations for transfection. An isopropyl modified polypiperazine is highly efficient over a wide range of concentrations outperforming linear polyethylenimine (l-PEI, 25 kDa) in regions of low N*/P ratios. A quantitative polymerase chain reaction (qPCR) surprisingly revealed that the pDNA within the piperazine-based polyplexes can be amplified in contrast to polyplexes based on l-PEI. The pDNA must therefore be more accessible and bound differently than for other known transfection polymers. Considering the various opportunities to further optimize their structure, polypiperazines represent a promising platform for designing effective soluble polymeric vectors, which are charge-neutral at physiological conditions. 相似文献
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Halofluorination of norbornadiene with N-bromosuccinimide, N-chlorosuccinimide or xenon difluoride in the presence of polyhydrogen fluoride-pyridine resulted in the formation of three products: 3-endo-halo-5-exo-fluoro (2) and 3-exo-halo-5-exo-fluoronortricyclane (3), and 2-exo-fiuoro-7-syn-halo-norbornene-5 (4). The exo-attack of the electrophile on norbornadiene is slightly predominant (65% X = Br, 64% X = Cl, 73% X = F) over the endo-attack. The Meerwein-Wagner rearrangement occurred only in the case of chlorine or fluorine halosubstituents of β-carbonium ions formed by exo attack of the electrophile. 相似文献
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Highly porous interpolymer ion-exchange membranes have been prepared from poly(styrene sulfonic acid), PSSA and poly(vinylidene fluoride) PVdF using a casting solvent of dimethylformamide and hexamethylphosphoramide. The membranes have been characterized by their water content, concentration potential, ionic conductivity, and their hydraulic permeability. An estimation of the porosity of the membranes has been made from the relative conductance of the potassium and the tetrabutylammonium ions in the film. This porosity has been compared with that derived from a consideration of the water flux through a Poiseuille-type pore. 相似文献
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