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991.
Ekta Mishra Jill L. Worlinsky Christian Brückner Victor Ryzhov 《Journal of the American Society for Mass Spectrometry》2014,25(1):18-29
Free base and cobalt(II) complexes of six meso-tetraphenylporphyrinoids containing nonpyrrolic heterocycles and of three meso-thienylporphyrins were investigated using electrospray ionization tandem mass spectrometry (ESI-MS/MS). Their fragmentation was studied in a quadrupole ion trap as a function of the porphyrinoid macrocycle structure and compared with the fragmentation behavior of the benchmark compound meso-tetraphenylporphyrin. In situ oxidation of the neutral cobalt(II) complexes under ESI conditions produced singly charged cobalt(III) porphyrinoid ions; the free bases were ionized by protonation. For the porphyrinoids with an intact porphyrin core, the major fragmentation pathways observed were the losses of the meso-substituent (for meso-phenyl groups) and characteristic fragmentations of one or more meso-substituents (for the meso-thienyl group). Complex fragmentation pathways were observed for porphyrinoids with modifications to the porphyrin core but chemically reasonable structures could be assigned to most fragments, thus delineating general patterns for the behavior of pyrrole-modified porphyrins under CID conditions. Figure
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992.
Cell Tracking with Caged Xenon: Using Cryptophanes as MRI Reporters upon Cellular Internalization 下载免费PDF全文
Stefan Klippel Jörg Döpfert Dr. Jabadurai Jayapaul Martin Kunth Federica Rossella Matthias Schnurr Dr. Christopher Witte Dr. Christian Freund Dr. Leif Schröder 《Angewandte Chemie (International ed. in English)》2014,53(2):493-496
Caged xenon has great potential in overcoming sensitivity limitations for solution‐state NMR detection of dilute molecules. However, no application of such a system as a magnetic resonance imaging (MRI) contrast agent has yet been performed with live cells. We demonstrate MRI localization of cells labeled with caged xenon in a packed‐bed bioreactor working under perfusion with hyperpolarized‐xenon‐saturated medium. Xenon hosts enable NMR/MRI experiments with switchable contrast and selectivity for cell‐associated versus unbound cages. We present MR images with 103‐fold sensitivity enhancement for cell‐internalized, dual‐mode (fluorescence/MRI) xenon hosts at low micromolar concentrations. Our results illustrate the capability of functionalized xenon to act as a highly sensitive cell tracer for MRI detection even without signal averaging. The method will bridge the challenging gap for translation to in vivo studies for the optimization of targeted biosensors and their multiplexing applications. 相似文献
993.
Back Cover: Cell Tracking with Caged Xenon: Using Cryptophanes as MRI Reporters upon Cellular Internalization (Angew. Chem. Int. Ed. 2/2014) 下载免费PDF全文
994.
A Strategy for the Preparation of Thioantimonates Based on the Concept of Weak Acids and Corresponding Strong Bases 下载免费PDF全文
Carolin Anderer Natalie Delwa de Alarcón Prof. Dr. Christian Näther Prof. Dr. Wolfgang Bensch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16953-16959
By following a new synthetic approach, which is based on the in situ formation of a basic medium by the reaction between the strong base Sb(V)S43? and the weak acid H2O, it was possible to prepare three layered thioantimonate(III) compounds of composition [TM(2,2′‐bipyridine)3][Sb6S10] (TM=Ni, Fe) and [Ni(4,4′‐dimethyl‐2,2′‐bipyridine)3][Sb6S10] under hydrothermal conditions featuring two different thioantimonate(III) network topologies. The antimony source, Na3SbS4 ? 9 H2O, undergoes several decomposition reactions and produces the SbIIIS3 species, which condenses to generate the layered anion. The application of transition‐metal complexes avoids crystallization of dense phases. The reactions are very fast compared to conventional hydrothermal/solvothermal syntheses and are much less sensitive to changes of the reaction parameters. 相似文献
995.
Lead Structures for New Antibacterials: Stereocontrolled Synthesis of a Bioactive Muraymycin Analogue 下载免费PDF全文
Daniel Wiegmann Dr. Stefan Boettcher Agnes Mihalyi Prof. Timothy D. H. Bugg Prof. Christian Ducho 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15292-15297
Naturally occurring muraymycin nucleoside antibiotics represent a promising class of novel antibacterial agents. The structural complexity suggests the investigation of simplified analogues as potential lead structures, which can then be further optimized towards highly potent antimicrobials. Herein we report studies on muraymycin‐derived potential lead structures lacking an aminoribose motif found in most naturally occurring muraymycins. We have identified a 5′‐defunctionalized motif to be ideal in terms of stability and chemical accessibility and have synthesized a full‐length muraymycin analogue based on this structure using a novel fully stereocontrolled route. The obtained 5′‐deoxy analogue of the natural product muraymycin C4 showed good inhibitory properties towards the bacterial target protein MraY, sufficient pharmacokinetic stability and no cytotoxicity against human cells, thus making it a promising lead for antibacterial drug development. 相似文献
996.
Pyranoside‐into‐Furanoside Rearrangement: New Reaction in Carbohydrate Chemistry and Its Application in Oligosaccharide Synthesis 下载免费PDF全文
Dr. Vadim B. Krylov Dmitry A. Argunov Dmitry Z. Vinnitskiy Stella A. Verkhnyatskaya Dr. Alexey G. Gerbst Dr. Nadezhda E. Ustyuzhanina Dr. Andrey S. Dmitrenok Prof. Dr. Johannes Huebner Prof. Dr. Otto Holst Prof. Dr. Hans‐Christian Siebert Prof. Dr. Nikolay E. Nifantiev 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16516-16522
Great interest in natural furanoside‐containing compounds has challenged the development of preparative methods for their synthesis. Herein a novel reaction in carbohydrate chemistry, namely a pyranoside‐into‐furanoside (PIF) rearrangement permitting the transformation of selectively O‐substituted pyranosides into the corresponding furanosides is reported. The discovered process includes acid‐promoted sulfation accompanied by rearrangement of the pyranoside ring into a furanoside ring followed by solvolytic O‐desulfation. This process, which has no analogy in organic chemistry, was shown to be a very useful tool for the synthesis of furanoside‐containing complex oligosaccharides, which was demonstrated by synthesizing disaccharide derivatives α‐D ‐Galp‐(1→3)‐β‐D ‐ Galf ‐OPr, 3‐O‐s ‐lactyl‐β‐D ‐ Galf ‐(1→3)‐β‐D ‐Glcp‐OPr, and α‐L ‐ Fucf ‐(1→4)‐β‐D ‐GlcpA‐OPr related to polysaccharides from the bacteria Klebsiella pneumoniae and Enterococcus faecalis and the brown seaweed Chordaria flagelliformis. 相似文献
997.
Highly Tin‐Selective Stille Coupling: Synthesis of a Polymer Containing a Stannole in the Main Chain 下载免费PDF全文
Julian Linshoeft Evan J. Baum Andreas Hussain Dr. Paul J. Gates Prof. Dr. Christian Näther Prof. Dr. Anne Staubitz 《Angewandte Chemie (International ed. in English)》2014,53(47):12916-12920
The incorporation of heavier Group 14 element heteroles into semiconducting polymers leads to unusual optoelectronic properties. However, polymers containing stannoles have not been accessible to date. We report a synthetic route to a well‐defined, stannole‐containing polymer, the first example of this class of π‐conjugated polymers. This route was made possible by developing difunctionalized stannole monomers and highly tin‐selective Stille coupling reactions that leave the tin in the stannole untouched. Compared to poly(3‐n‐hexylthiophene), the resulting polymer displays a remarkable bathochromic shift in its absorption. 相似文献
998.
Dr. Roberto J. Brea Christian M. Cole Prof. Neal K. Devaraj 《Angewandte Chemie (International ed. in English)》2014,53(51):14102-14105
Phospholipid vesicles are of intense fundamental and practical interest, yet methods for their de novo generation from reactive precursors are limited. A non‐enzymatic and chemoselective method to spontaneously generate phospholipid membranes from water‐soluble starting materials would be a powerful tool for generating vesicles and studying lipid membranes. Here we describe the use of native chemical ligation (NCL) to rapidly prepare phospholipids spontaneously from thioesters. While NCL is one of the most popular tools for synthesizing proteins and nucleic acids, to our knowledge this is the first example of using NCL to generate phospholipids de novo. The lipids are capable of in situ synthesis and self‐assembly into vesicles that can grow to several microns in diameter. The selectivity of the NCL reaction makes in situ membrane formation compatible with biological materials such as proteins. This work expands the application of NCL to the formation of phospholipid membranes. 相似文献
999.
Formation of “Quasi” Contact or Solvent‐separated Ion Pairs in the Local Environment of Probe Molecules Dissolved in Ionic Liquids 下载免费PDF全文
Matthias Strauch Dr. Christian Roth Falk Kubatzki Prof. Dr. Ralf Ludwig 《Chemphyschem》2014,15(2):265-270
The change from “quasi” contact to “quasi” solvent‐separated ion‐pair configuration in the local environment of a probe molecule in ionic liquids depends on the varying interaction strength of the chosen anions. The ion speciation in these Coulomb fluids could be shown by combining infrared spectroscopy, density functional theory calculations, and natural bond orbital analysis using a low‐self‐clustering probe molecule. 相似文献
1000.
Christian Voss 《Adsorption》2014,20(2-3):295-299
CO2 removal from gaseous streams is one of the most important separation tasks in this decade. Adsorption processes can contribute in a wide range to this topic, thus an enormous effort is performed respectively in research and industry. In two scenarios the competitiveness of pressure swing adsorption (PSA) and vacuum pressure swing adsorption technology is assessed: Carbon capture from hydrogen production by steam methane reforming for enhanced oil recovery and CO2 removal from direct reduction processes for iron making. Additionally, industrial requirements, project as well as operation driven, have to be considered. Robustness and stable operation is as important as optimized captial expenditure and operational expenditure. Considering economical and operational aspects PSA processes are the most attractive alternatives in the presented scenarios. 相似文献