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941.
Approach to the study of flavone di‐C‐glycosides by high performance liquid chromatography‐tandem ion trap mass spectrometry and its application to characterization of flavonoid composition in Viola yedoensis
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Jie Cao Chengle Yin Yan Qin Zhihong Cheng Daofeng Chen 《Journal of mass spectrometry : JMS》2014,49(10):1010-1024
The mass spectrometric (MS) analysis of flavone di‐C‐glycosides has been a difficult task due to pure standards being unavailable commercially and to that the reported relative intensities of some diagnostic ions varied with MS instruments. In this study, five flavone di‐C‐glycoside standards from Viola yedoensis have been systematically studied by high performance liquid chromatography‐electrospray ionization‐tandem ion trap mass spectrometry (HPLC‐ESI‐IT‐MSn) in the negative ion mode to analyze their fragmentation patterns. A new MS2 and MS3 hierarchical fragmentation for the identification of the sugar nature (hexoses or pentoses) at C‐6 and C‐8 is presented based on previously established rules of fragmentation. Here, for the first time, we report that the MS2 and MS3 structure‐diagnostic fragments about the glycosylation types and positions are highly dependent on the configuration of the sugars at C‐6 and C‐8. The base peak (0,2X10,2X2? ion) in MS3 spectra of di‐C‐glycosides could be used as a diagnostic ion for flavone aglycones. These newly proposed fragmentation behaviors have been successfully applied to the characterization of flavone di‐C‐glycosides found in V. yedoensis. A total of 35 flavonoid glycosides, including 1 flavone mono‐C‐hexoside, 2 flavone 6,8‐di‐C‐hexosides, 11 flavone 6,8‐di‐C‐pentosides, 13 flavone 6,8‐C‐hexosyl‐C‐pentosides, 5 acetylated flavone C‐glycosides and 3 flavonol O‐glycosides, were identified or tentatively identified on the base of their UV profiles, MS and MSn (n = 5) data, or by comparing with reference substances. Among these, the acetylated flavone C‐glycosides were reported from V. yedoensis for the first time. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
942.
HF:H2O2:H2O solution (40%wt.HF: 30wt.%H2O2: H2O, 3:2:1 by volume) was used to reveal extended defects (line, face and volume defects) in bulk ZnTe crystals grown from Te solution. The etch patterns were analyzed based on their size, shape and distribution. The etch figures, both in the shape of pits and hillocks with high resolution, show forms controlled by the symmetries of the respective faces were produced. Two different sizes of pits were observed, the larger‐size pits correspond to dislocations penetrating the surface, however, the smaller‐size texture pits are produced on the defect‐free region, which serve as standard pits on respect faces. The face defects, such as grain boundaries, sub‐grain boundaries, dislocation walls, twins and stacking faults, can be all displayed clearly. Another essential feature of the etchant is that, it can effectively dissolve Te‐rich phase (Te inclusion/precipitates), which makes it promising to reveal the shape of this volume defect. 相似文献
943.
Fangyang Liu Can Han Liangxing Jiang Jie Li Yexiang Liu 《Journal of Solid State Electrochemistry》2014,18(7):1833-1845
Based on the basic principles of kinetics and some reasonable assumptions about the electrodeposition process, a dynamic model for metal selenide electrodeposition (kink site selected model) was constructed. This model is of universal significance in realizing the compositional prediction and dynamic behavior analysis of deposited films for different main salt concentration ratios and was applied to the ternary Cu–In–Se system. For CuInSe2 electrodeposition, in the Cu–Se system, the co-deposition of Cu and Se can be carried out within a large range of main salt concentration ratio; in the Cu–In system, the mole fraction of Cu in deposited thin films is always higher than that of Cu2+ in electrolyte, while in the In–Se system, the co-deposition of In and Se can be achieved only when the In3+ concentration is much higher than the H2SeO3 concentration. As for the compositional estimation of CuInSe2, the predictive results of our dynamic model agree well with the experimental data. It is then found that by correcting the difference of kink site selectivity constants caused by the change of deposition potential, the error of the predictive results can be reduced. 相似文献
944.
Metal‐Free Aminosulfonylation of Aryldiazonium Tetrafluoroborates with DABCO⋅(SO2)2 and Hydrazines
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Danqing Zheng Yuanyuan An Dr. Zhenhua Li Prof. Dr. Jie Wu 《Angewandte Chemie (International ed. in English)》2014,53(9):2451-2454
The coupling of aryldiazonium tetrafluoroborates, DABCO?(SO2)2, and hydrazines under metal‐free conditions leads to the formation of aryl N‐aminosulfonamides. The reaction proceeds smoothly at room temperature and shows broad functional‐group tolerance. A radical process is proposed for this transformation. 相似文献
945.
Hexafluoroantimonic Acid Catalysis: Formal [3+2+2] Cycloaddition of Aziridines with Two Alkynes
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Ming‐Bo Zhou Ren‐Jie Song Prof. Dr. Jin‐Heng Li 《Angewandte Chemie (International ed. in English)》2014,53(16):4196-4199
A practical method for the synthesis of azepine derivatives, a typical seven‐membered heterocyclic ring system, was developed and involves the use of hexafluoroantimonic acid to catalyze a formal [3+2+2] cycloaddition of aziridines with two alkynes. This method was applicable to two of the same or different terminal alkynes for the [3+2+2] cycloaddition with unactivated aziridines, and furnished the corresponding azepine derivatives in good yields with good levels of chemo‐ and regioselectivity. The mechanism was also discussed according to the results of the in situ HRMS and 1H NMR analysis. 相似文献
946.
Dr. Jie Liang Dr. Jie Su Prof. Yingxia Wang Yanping Chen Prof. Xiaodong Zou Fuhui Liao Prof. Jianhua Lin Prof. Junliang Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(49):16097-16101
A germanate zeolite, PKU‐14, with a three‐ dimensional large‐pore channel system was structurally characterized by a combination of high‐resolution powder X‐ray diffraction, rotation electron diffraction, NMR, and IR spectroscopy. Ordered Ge4O4 vacancies inside the [46.612] cages has been found in PKU‐14, in which a unique (H2O)2 dimer was located at the vacancies and played a structure‐directing role. It is the first time that water clusters are found to be templates for ordered framework vacancies. 相似文献
947.
Photochemically Engineering the Metal–Semiconductor Interface for Room‐Temperature Transfer Hydrogenation of Nitroarenes with Formic Acid
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Dr. Xin‐Hao Li Yi‐Yu Cai Ling‐Hong Gong Dr. Wei Fu Dr. Kai‐Xue Wang Dr. Hong‐Liang Bao Dr. Xiao Wei Dr. Jie‐Sheng Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16732-16737
A mild photochemical approach was applied to construct highly coupled metal–semiconductor dyads, which were found to efficiently facilitate the hydrogenation of nitrobenzene. Aniline was produced in excellent yield (>99 %, TOF: 1183) using formic acid as hydrogen source and water as solvent at room temperature. This general and green catalytic process is applicable to a wide range of nitroarenes without the involvement of high‐pressure gases or sacrificial additives. 相似文献
948.
Coverage‐ and Temperature‐Dependent Metalation and Dehydrogenation of Tetraphenylporphyrin on Cu(111)
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Michael Röckert Matthias Franke Quratulain Tariq Stefanie Ditze Michael Stark Patrick Uffinger Daniel Wechsler Upendra Singh Dr. Jie Xiao Dr. Hubertus Marbach Prof. Dr. Hans‐Peter Steinrück Dr. Ole Lytken 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):8948-8953
Using temperature‐programmed desorption, supported by X‐ray photoelectron spectroscopy and scanning tunneling microscopy, a comprehensive overview of the main reactions of 5,10,15,20‐tetraphenyl‐21H,23H‐porphyrin (2HTPP) on Cu(111) as a function of coverage and temperature is obtained. Three reactions were identified: metalation with Cu substrate atoms, stepwise partial dehydrogenation, and finally complete dehydrogenation. At low coverage the reactions are independent of coverage, but at higher coverage metalation becomes faster and partial dehydrogenation slower. This behavior is explained by a weaker interaction between the iminic nitrogen atoms and the Cu(111) surface in the high‐coverage checkerboard structure, leading to faster metalation, and the stabilizing effect of T‐type interactions in the CuTPP islands formed at high coverage after metalation, leading to slower dehydrogenation. Based on the amount of hydrogen released and the appearance in STM, a structure of the partially dehydrogenated molecule is suggested. 相似文献
949.
Changduo Pan Ablimit Abdukader Jie Han Prof. Dr. Yixiang Cheng Prof. Dr. Chengjian Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3606-3609
A ruthenium‐catalyzed direct C7 amidation of indoline C?H bonds with sulfonyl azides was developed. This procedure allows the synthesis of a variety of 7‐amino‐substituted indolines, which are useful in pharmaceutical. The good functional tolerances, as well as the mild conditions, are prominent feature of this method. 相似文献
950.
Tailoring 3,3′‐Dihydroxyisorenieratene to Hydroxystilbene: Finding a Resveratrol Analogue with Increased Antiproliferation Activity and Cell Selectivity
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Yan‐Fei Kang Wen‐Jing Yan Ting‐Wen Zhou Dr. Fang Dai Dr. Xiu‐Zhuang Li Xia‐Zhen Bao Yu‐Ting Du Cui‐Hong Yuan Hai‐Bo Wang Xiao‐Rong Ren Dr. Qiang Liu Dr. Xiao‐Ling Jin Prof. Dr. Bo Zhou Prof. Dr. Jie Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):8904-8908
Four novel compounds were designed by “tailoring” 3,3′‐dihydroxyisorenieratene (a natural carotenoid) based on an isoprene unit retention truncation strategy. Among them, the smallest molecule 1 (2,3,6,2′,3′,6′‐hexamethyl‐4,4′‐dihydroxy‐trans‐stilbene) was concisely synthesized in a one‐pot Stille–Heck tandem sequence, and surfaced as a promising lead molecule in terms of its selective antiproliferative activity mediated by blocking the NCI‐H460 cell cycle in G1 phase. Additionally, theoretical calculations and cell uptake experiments indicate that the unique polymethylation pattern of compound 1 significantly induces a conformational change shift out of planarity and increases its cell uptake and metabolic stability. The observation should be helpful to rationally design resveratrol‐inspired antiproliferative agents. 相似文献