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101.
Jean-Claude Prome Hlne Aurelle Danielle Prome Arlette Savagnac 《Journal of mass spectrometry : JMS》1987,22(1):6-12
The oxyanion [M? H]? from several methylglycosides were generated by fast atom bombardment and their decomposition was studied by mass-analysed ion kinetic energy spectrometry. The main decomposition pathway is the loss of methanol. The hydroxylic hydrogen arises by proton transfer from the hydroxyl groups of the sugar. In the gluco-series, no anomeric effect is found. The absence of either the hydroxyl groups at C-2 or C-6 does not inhibit the glycosidic cleavage. However, the blocking of both the hydroxyl groups at C-4 and C-6, by a benzylidene group or two methyl groups, inhibit completely the glycosidic cleavage. From these results, it is proposed that the glycosidic cleavage occurs after opening the sugar ring by a vicinal attack of an oxyanion at C-6 or C-4 to the C-5 carbon atom. Then, the ionized hemi-acetals fragment into a methanolate anion and a 5,6- or 4,5-anhydrosugar which exchange another proton before their separation into charged and neutral species. 相似文献
102.
Charles W. Jefford Danielle Jaggi Shigeo Kohmoto John Boukouvalas Grald Bernardinelli 《Helvetica chimica acta》1984,67(8):2254-2260
Summary The reaction of 4,5-dimethyl-4-hydroperoxy-1(4H)-nephthalenone ( 9 ) with acetaldehyde, pivalaldehyde, benzaldehyde, and p-chlorobenzaldehyde in CH2Cl2 in the presence of Amberlyst-15 as catalyst gave the corresponding cis-3-methyl, t -butyl, phenyl and p -chlorophenyl derivatives of 10,10b-dimethylnaphtono[2,1-e][1,2,4]trioxin-6(5)H-one in 80-95% yields. Acetone reacted similarly with 9 to give the 3,3′ -dimethyl derivative. Configurations of all trioxinones were assigned by comparison of their spectral properties with that of the p -chloro derivative whose structure was determined by X-ray. 2,5-Diphenyl-2-hydroperoxypyrrole was less efficient that 9 , but it condensed with acetaldehyde and pivaladehyde under the same conditions giving the cis - 3-methyl and cis - 3-(t -butyl) derivatives of 6,7a-diphenyl-4a, 7a-dihydro-3H, 5H -[1,2,4]trio-xino[3,2-e]pyrrole in 24 and 20% yield, respectively. 相似文献
103.
Experimental and Theoretical Study of the Reactivity of Gold Nanoparticles Towards Benzimidazole‐2‐ylidene Ligands 下载免费PDF全文
Dr. María Rodríguez‐Castillo Gustavo Lugo‐Preciado Dr. Danielle Laurencin Dr. Frederik Tielens Dr. Arie van der Lee Dr. Sébastien Clément Dr. Yannick Guari Dr. José M. López‐de‐Luzuriaga Dr. Miguel Monge Dr. Françoise Remacle Dr. Sébastien Richeter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10446-10458
The reactivity of benzimidazol‐2‐ylidenes with respect to gold nanoparticles (AuNPs) has been investigated using a combined experimental and computational approach. First, the grafting of benzimidazol‐2‐ylidenes bearing benzyl groups on the nitrogen atoms is described, and comparisons are made with structurally similar N‐heterocyclic carbenes (NHCs) bearing other N‐groups. Similar reactivity was observed for all NHCs, with 1) the erosion of the AuNPs under the effect of the NHC and 2) the formation of bis(NHC) gold complexes. DFT calculations were performed to investigate the modes of grafting of such ligands, to determine adsorption energies, and to rationalize the spectroscopic data. Two types of computational models were developed to describe the grafting onto large or small AuNPs, with either periodic or cluster‐type DFT calculations. Calculations of NMR parameters were performed on some of these models, and discussed in light of the experimental data. 相似文献
104.
105.
Revannath Sutar Danielle Butilkov N. Gabriel Lemcoff 《Journal of Coordination Chemistry》2018,71(11-13):1715-1727
AbstractLatent metathesis catalysts equipped with boronate esters of diols as exchangeable end-groups on their NHC ligands and an S-chelated ruthenium-benzylidene core were synthesized. The stable S-chelated ruthenium complexes underwent hydrolysis under mild acidic conditions, allowing easy exchange of terminal units by several 1,2- and 1,3-diols, without degrading the central ruthenium benzylidene. Using this strategy, we also prepared metathesis catalysts equipped with diallyl substrates at the termini that showed concentration dependency on RCM reactions. Notably, the larger dendritic catalysts were more efficient at the more dilute condition. 相似文献
106.
Danielle Bury Guy Faust Maria Paraskevaidi Katherine M. Ashton Timothy P. Dawson 《Analytical letters》2019,52(4):575-587
Metastatic brain tumors represent a significant proportion of tumors identified intraoperatively. A rapid diagnostic method, circumventing the need for histopathology studies, could prove clinically useful. As many spectroscopic studies have shown ability to differentitate between different tumor types, this technique was evaluated for use within metastatic brain tumors. Spectrochemical approaches [Raman and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) spectroscopy] were applied to determine how readily they may identify the primary site for the metastatic tumor. Metastases were from primary adenocarcinomas of lung (n?=?7) and colorectum (n?=?7), and for comparison, metastatic melanoma (n?=?7). The objective was to determine if Raman or ATR-FTIR spectroscopy could delineate the origin of the primary tumor. The results demonstrate that there are marked similarities between the two adenocarcinoma groups and whilst Raman and ATR-FTIR can distinguish the three groups with limited success, classification accuracy is greatly improved when combining the adenocarcinoma groups. The use of such techniques in the clinical setting is more likely to be found intraoperatively, determining the presence of a tumor and suggesting the tumor class; however, traditional histopathology would still be needed to identify the primary origin of the tumor. 相似文献
107.
de Melo Anely Maciel Barbi Rafaela Cristina Turola Costa Bruno Patrício Ikeda Mônica Alves Fillemon Edillyn Silva Bambirra Carpiné Danielle Ribani Rosemary Hoffmann 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12313-12328
Journal of Thermal Analysis and Calorimetry - Despite their being rich in bioactive compounds, by-products produced during fruit pulping are usually discarded. The present paper aimed to... 相似文献
108.
109.
Mahmoud Karimi Paul Croaker Alex Skvortsov Danielle Moreau Nicole Kessissoglou 《国际流体数值方法杂志》2019,90(10):522-543
An efficient hybrid uncorrelated wall plane waves–boundary element method (UWPW-BEM) technique is proposed to predict the flow-induced noise from a structure in low Mach number turbulent flow. Reynolds-averaged Navier-Stokes equations are used to estimate the turbulent boundary layer parameters such as convective velocity, boundary layer thickness, and wall shear stress over the surface of the structure. The spectrum of the wall pressure fluctuations is evaluated from the turbulent boundary layer parameters and by using semi-empirical models from literature. The wall pressure field underneath the turbulent boundary layer is synthesized by realizations of uncorrelated wall plane waves (UWPW). An acoustic BEM solver is then employed to compute the acoustic pressure scattered by the structure from the synthesized wall pressure field. Finally, the acoustic response of the structure in turbulent flow is obtained as an ensemble average of the acoustic pressures due to all realizations of uncorrelated plane waves. To demonstrate the hybrid UWPW-BEM approach, the self-noise generated by a flat plate in turbulent flow with Reynolds number based on chord Rec = 4.9 × 105 is predicted. The results are compared with those obtained from a large eddy simulation (LES)-BEM technique as well as with experimental data from literature. 相似文献
110.