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991.
Acceptor Reactivity in the Total Synthesis of Alginate Fragments Containing α‐L‐Guluronic Acid and β‐D‐Mannuronic Acid
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Qingju Zhang Erwin R. van Rijssel Marthe T. C. Walvoort Herman S. Overkleeft Gijsbert A. van der Marel Jeroen D. C. Codée 《Angewandte Chemie (International ed. in English)》2015,54(26):7670-7673
The total synthesis of mixed‐sequence alginate oligosaccharides, featuring both β‐D ‐mannuronic acid (M) and α‐L ‐guluronic acid (G), is reported for the first time. A set of GM, GMG, GMGM, GMGMG, GMGMGM, GMGMGMG, and GMGGMG alginates was assembled using GM building blocks, having a guluronic acid acceptor part and a mannuronic acid donor side to allow the fully stereoselective construction of the cis‐glycosidic linkages. It was found that the nature of the reducing‐end anomeric center, which is ten atoms away from the reacting alcohol group in the key disaccharide acceptor, had a tremendous effect on the efficiency with which the building blocks were united. This chiral center determines the overall shape of the acceptor and it is revealed that the conformational flexibility of the acceptor is an all‐important factor in determining the outcome of a glycosylation reaction. 相似文献
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Abstract The energetic aspects of layer deformation in ferroelectric liquid crystal cells are discussed and the actual chevron shape is calculated in some situations. We emphasize two, in our view, essential energy contributions. One term considers the layer curvature. The other one refers to the variations in the distance between layers and the consequent changes of the smectic cone angle. In some simple cases we can determine optimal shapes of the chevron layer structure by analytical solutions, based on these two energy terms. In more complicated situations other contributions have to be considered and the chevron profiles are simulated numerically. The influence of the applied voltage and the choice of parameter values are studied. 相似文献
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Audrey Moudens Abdessamad Benidar M. Herman Bertrand Plez 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(3):540-549
Recently, a high temperature source has been used to produce high temperature emission spectra of acetylene in the 3 μm spectral range, under Doppler limited resolution, and the complete spectral assignment has been performed using a global rovibrational Hamiltonian [Amyay B, Robert S, Herman M, Fayt A, Raghavendra B, Moudens A et al. Vibration-rotation pattern in acetylene (II): Introduction to Coriolis coupling in the global model and analysis of emission spectra of hot acetylene around 3 μm. J Chem Phys 2009;131:114301]. The present investigation focuses on the relative emission line intensities which are observed to be affected. The strongest lines intensity may be considerably reduced for high column density acetylene samples, hence affecting the 3:1 ortho:para intensity ratio. A radiative model is developed to take into account the effects generated by the strong opacity of the acetylene samples including self-absorption and absorption of the radiation emitted by the hot environment. The model is used to extract the absolute concentration of the high temperature acetylene samples from the observed relative spectral intensities. The relevance of the procedure for infrared remote sensing in high temperature astrophysical environments, such as circumstellar envelopes of cool carbon rich evolved stars, is discussed. 相似文献
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Maxwell D. Cummings Jimmy Lindberg Tse‐I Lin Herman de Kock Oliver Lenz Elisabet Lilja Sara Felländer Vera Baraznenok Susanne Nyström Magnus Nilsson Lotta Vrang Michael Edlund Åsa Rosenquist Bertil Samuelsson Pierre Raboisson Kenneth Simmen 《Angewandte Chemie (International ed. in English)》2010,49(9):1652-1655
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M. Sc. Marc P. Baggelaar M. Sc. Freek J. Janssen Annelot C. M. van Esbroeck Ing. Hans den Dulk M. Sc. Marco Allarà M. Sc. Sascha Hoogendoorn Dr. Ross McGuire Dr. Bogdan I. Florea Ing. Nico Meeuwenoord Ing. Hans van den Elst Prof. Dr. Gijsbert A. van der Marel Prof. Dr. Jaap Brouwer Prof. Dr. Vincenzo Di Marzo Prof. Dr. Herman S. Overkleeft Dr. Mario van der Stelt 《Angewandte Chemie (International ed. in English)》2013,52(46):12193-12193
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