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61.
Vladimir A. Alfonsov Charles E. McKenna Evgenia V. Bayandina Boris A. Kashemirov Liliya N. Yarmieva Lyudmila N. Punegova Olga N. Kataeva 《Heteroatom Chemistry》2008,19(6):575-582
The paper describes a simple, direct synthesis of enantiopure cyclic α‐aminophosphonic acids on the basis of silyldealkylation and followed by hydrolysis of the parent diastereoisomeric cyclic 1,4,2‐oxazaphosphorines, which have been obtained by intramolecular stereospecific nucleophilic addition of phosphites to imines. In this approach, the high diastereoselectivity of the stereocontrolling penultimate step is preserved by conversion of the intermediate ester to the final phosphonic acid under very mild, nonracemizing conditions. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:575–582, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20480 相似文献
62.
Karousou EG Militsopoulou M Porta G De Luca G Hascall VC Passi A 《Electrophoresis》2004,25(17):2919-2925
This report describes a new formulation of polyacrylamide gel electrophoresis of fluorophore-labeled saccharides (PAGEFS) for the analysis of hyaluronan (HA) and chondroitin sulfate (CS) Delta-disaccharides. PAGEFS relies on derivatization of reducing ends of HA- and the variously sulfated CS-derived Delta-disaccharides with 2-aminoacridone (AMAC), followed by electrophoresis under optimized buffer conditions (Tris-borate and Tris-HCl) and on polyacrylamide gels (25% T/3.75% C). The method was applied to the analysis of glycosaminoglycans (GAGs) from the human umbilical cord tissue and GAGs isolated from human aortic smooth muscle cell cultures. The obtained results were in agreement with those obtained after an analysis with high-performance liquid chromatography (HPLC). On the basis of these results, PAGEFS is a rapid and sensitive method for the analysis of the total amount of HA- and CS-derived disaccharides, as it allows analyzing 20 samples in minigels in one run and provides quantitation with relatively high sensitivity (less than 25 pmol per disaccharide). In addition, PAGEFS overcomes the lack of commercial gels described previously for the separation of AMAC-labeled disaccharides. Therefore, the method proposed here is an economic and useful tool for a fast screening of GAGs in biological samples, particularly when a high number of samples should be analyzed. 相似文献
63.
Zabolotskaya EA Ilinskii YA Meegan GD Hamilton MF 《The Journal of the Acoustical Society of America》2005,118(4):2173-2181
A model equation for the oscillation of a pressurized gas bubble in a nonlinear incompressible elastic medium [Emelianov et al., J. Acoust. Soc. Am. 115, 581 (2004)] is extended to include effects of surface tension, viscosity, weak compressibility, and confinement by an elastic shell. The significance of this work is that starting from first principles, the full nonlinearity of the incompressible elastic medium surrounding the bubble and forming its shell is taken into account. Measurements of equilibrium radius as a function of external pressure for a gas bubble in a tissue-like gel are also presented. A general approach to including hysteresis is also discussed. 相似文献
64.
Dmitriy N. Shurpik Denis A. Sevastyanov Pavel V. Zelenikhin Evgenia V. Subakaeva Vladimir G. Evtugyn Yuriy N. Osin Peter J. Cragg Ivan I. Stoikov 《Tetrahedron letters》2018,59(50):4410-4415
Hydrazides of glycine-containing decasubstituted pillar[5]arenes were synthesized and characterized. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed that self-assembly into monodisperse spherical nanoparticles (28?nm) was typical in water for pillarene hydrazides containing glycylglycide fragments (1?×?10?3?M). Binding of the antitumor drug Floxuridine in water by the substituents of the macrocycle was established by NMR spectroscopy. It was shown by DLS and TEM, that heating the macrocycle-Floxuridine system in a 1:1 ratio at 1?×?10?4?M led to its self-organization into monodisperse spherical particles 132?nm in diameter. 相似文献
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Ji Ma Yubin Fu Evgenia Dmitrieva Fupin Liu Hartmut Komber Felix Hennersdorf Alexey A. Popov Jan J. Weigand Junzhi Liu Xinliang Feng 《Angewandte Chemie (International ed. in English)》2020,59(14):5637-5642
Three unprecedented helical nanographenes ( 1 , 2 , and 3 ) containing an azulene unit are synthesized. The resultant helical structures are unambiguously confirmed by X‐ray crystallographic analysis. The embedded azulene unit in 2 possesses a record‐high twisting degree (16.1°) as a result of the contiguous steric repulsion at the helical inner rim. Structural analysis in combination with theoretical calculations reveals that these helical nanographenes manifest a global aromatic structure, while the inner azulene unit exhibits weak antiaromatic character. Furthermore, UV/Vis‐spectral measurements reveal that superhelicenes 2 and 3 possess narrow energy gaps ( 2 : 1.88 eV; 3 : 2.03 eV), as corroborated by cyclic voltammetry and supported by density functional theory (DFT) calculations. The stable oxidized and reduced states of 2 and 3 are characterized by in‐situ EPR/Vis–NIR spectroelectrochemistry. Our study provides a novel synthetic strategy for helical nanographenes containing azulene units as well as their associated structures and physical properties. 相似文献
69.
Sebastian N. Intorp Manuel Hodecker Matthias Müller Olena Tverskoy Marco Rosenkranz Evgenia Dmitrieva Alexey A. Popov Frank Rominger Jan Freudenberg Andreas Dreuw Uwe H. F. Bunz 《Angewandte Chemie (International ed. in English)》2020,59(30):12396-12401
Quinoidal azaacenes with almost pure diradical character (y=0.95 to y=0.99) were synthesized. All compounds exhibit paramagnetic behavior investigated by EPR and NMR spectroscopy, and SQUID measurements, revealing thermally populated triplet states with an extremely low‐energy gap ΔEST′ of 0.58 to 1.0 kcal mol?1. The species are persistent in solution (half‐life≈14–21 h) and in the solid state they are stable for weeks. 相似文献
70.
Confocal Raman micro-spectral imaging (CRMI) is a relatively novel technique for the construction of label-free images of biological entities, such as cells or tissue sections. This method utilizes thousands of spatially resolved Raman spectra, and sophisticated image analysis algorithms, to construct images which are based strictly on the inherent biochemical abundance contrast afforded by Raman microscopy. Here, we apply this methodology to monitor the very early communication processes that occur in a growing stem cell colony, yielding information on biochemical composition during development processes of the early stages of embryogenesis. 相似文献