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191.
Harding M Hodgson R Majid T McDowall KJ Nelson A 《Organic & biomolecular chemistry》2003,1(2):338-349
Dipyranones, such as 1,2-bis[(2R,3S,6S)-3-hydroxy-6-methoxy-3-oxo-6H-pyran-2-yl]ethane, were exploited as templates for the synthesis of some novel C-linked disaccharide analogues. Efficient methods, such as stereoselective reduction and dihydroxylation, were developed for two-directional functionalisation of these templates. Peracetylated derivatives of ten stereoisomeric disaccharide analogues [acetic acid 4,5-diacetoxy-6-methoxy-[(3',4',5'-triacetoxy-6'-methoxytetrahydropyran- 2'-yl)ethyl]tetrahydropyran-3-yl esters] were synthesised from a virtual library of 136 compounds; furthermore, an additional eight stereoisomers could have been synthesised simply by using the enantiomeric ligand in the enantioselective step. The ability of (2S,3S,4R,5R,6R)-6-methoxy-2-[2'-((2'R,3'R,4'S, 5'R,6'S)-3',4',5'-trihydroxy-6'-methoxytetrahydropyran-2'-yl) ethyl]tetrahydropyran-3,4,5-triol to bind to the repressor protein, LacI, was estimated to be similar to that of isopropyl-beta-thiogalactoside. The disaccharide mimetics were concluded to be a new and interesting class of C-linked disaccharide mimetics with promising, though largely unstudied, biological activity. 相似文献
192.
Hodgson RJ 《Journal of colloid and interface science》2000,229(2):399-406
The inverse static light-scattering problem for spheres is treated numerically by employing genetic algorithms. Intensity functions are generated with variable amounts of noise and are used as input data in order to deduce both the refractive index and the radius of the particle. Both real and complex refractive indices are treated. Comparisons are made with a gradient-based minimization approach that requires fewer function evaluations but which often terminates in a local minimum. The genetic algorithm approach gives very good results for the parameters even in cases where the noise level in the data is relatively high. Copyright 2000 Academic Press. 相似文献
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195.
Lithiation-in situ silylation of terminal epoxides using lithium 2,2,6,6-tetramethylpiperidide in combination with phenyldimethyl(or diethyl)silyl chloride provides a direct process for the synthesis of trans-α,β-epoxysilanes, which undergo α-ring opening with alkenylcoppers to give syn-β-hydroxyallylic silanes. The chemistry is applied in an annulation approach to the C(10)-C(19) tetrahydrofuran-containing portion of the lytophilippines. 相似文献
196.
Cu K-edge extended X-ray absorption fine structure (EXAFS) and Minuit X-ray absorption near-edge structure (MXAN) analyses were combined to evaluate the structure of the copper(II) imidazole complex ion in liquid aqueous solution. Both methods converged to the same square-pyramidal inner coordination sphere [Cu(Im)(4)L(ax)](2+) (L(ax) indeterminate) with four equatorial nitrogen atoms at EXAFS, 2.02 ± 0.01 ?, and MXAN, 1.99 ± 0.03 ?. A short-axial N/O scatterer (L(ax)) was found at 2.12 ± 0.02 ? (EXAFS) or 2.14 ± 0.06 ? (MXAN). A second but very weak axial Cu-N/O interaction was found at 2.9 ± 0.1 ? (EXAFS) or 3.0 ± 0.1 ? (MXAN). In the MXAN fits, only a square-pyramidal structural model successfully reproduced the doubled maximum of the rising K-edge X-ray absorption spectrum, specifically excluding an octahedral model. Both EXAFS and MXAN also found eight outlying oxygen scatterers at 4.2 ± 0.3 ? that contributed significant intensity over the entire spectral energy range. Two prominent rising K-edge shoulders at 8987.1 and 8990.5 eV were found to reflect multiple scattering from the 3.0 ? axial scatterer and the imidazole rings, respectively. In the MXAN fits, the imidazole rings took in-plane rotationally staggered positions about copper. The combined (EXAFS and MXAN) model for the unconstrained cupric imidazole complex ion in liquid aqueous solution is an axially elongated square-pyramidal core, with a weak nonbonded interaction at the second axial coordination position and a solvation shell of eight nearest-neighbor water molecules. This core square-pyramidal motif has persisted through [Cu(H(2)O)(5)](2+), [Cu(NH(3))(4)(NH(3),H(2)O)](2+), (1, 2) and now [Cu(Im)(4)L(ax))](2+) and appears to be the geometry preferred by unconstrained aqueous-phase copper(II) complex ions. 相似文献
197.
Chen P DeBeer George S Cabrito I Antholine WE Moura JJ Moura I Hedman B Hodgson KO Solomon EI 《Journal of the American Chemical Society》2002,124(5):744-745
Spectroscopy coupled with density functional calculations has been used to define the spin state, oxidation states, spin distribution, and ground state wave function of the mu4-sulfide bridged tetranuclear CuZ cluster of nitrous oxide reductase. Initial insight into the electronic contribution to N2O reduction is developed, which involves a sigma superexchange pathway through the bridging sulfide. 相似文献
198.
The stability of OH on Pt(111) has been investigated to determine the role of hydrogen bonding in stabilizing the overlayer. We find that the optimal structure is a mixed (OH+H2O) phase, confirming recent density-functional theory predictions. The reaction O+3H(2)O forms a hexagonal (sqrt[3]xsqrt[3])R30 degrees -(OH+H2O) lattice with a weak (3x3) superstructure, caused by ordering of the hydrogen bonds. The mixed overlayer can accommodate a range of H(2)O/OH compositions but becomes less stable as the H2O content is reduced, causing defects in the hydrogen-bonding network that lift the (3 x 3) superstructure and destabilize the overlayer. 相似文献
199.
Enhancing the Electrochemical Performance of the LiMn2O4 Hollow Microsphere Cathode with a LiNi0.5Mn1.5O4 Coated Layer 下载免费PDF全文
Wei Liu Dr. Jun Liu Kunfeng Chen Dr. Shaomin Ji Yanling Wan Prof. Dr. Yichun Zhou Prof. Dr. Dongfeng Xue Prof. Dr. Peter Hodgson Dr. Yuncang Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):824-830
Spinel cathode materials consisting of LiMn2O4@LiNi0.5Mn1.5O4 hollow microspheres have been synthesized by a facile solution‐phase coating and subsequent solid‐phase lithiation route in an atmosphere of air. When used as the cathode of lithium‐ion batteries, the double‐shell LiMn2O4@LiNi0.5Mn1.5O4 hollow microspheres thus obtained show a high specific capacity of 120 mA h g?1 at 1 C rate, and excellent rate capability (90 mAhg?1 at 10 C) over the range of 3.5–5 V versus Li/Li+ with a retention of 95 % over 500 cycles. 相似文献
200.
Anomalous Nuclear Overhauser Effects in Carbon‐Substituted Aziridines: Scalar Cross‐Relaxation of the First Kind 下载免费PDF全文