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91.
《Arabian Journal of Chemistry》2022,15(11):104208
Dendrobium nobile alkaloids (DNLA) and glycosides are the main active components extracted from Dendrobium nobile Lindl. (D. nobile) used for thousands of years in China. The pharmacological effects of the above chemical components are significantly different. D. nobile is mainly grown at an altitude ranging from 230 to 800 m in Chishui City, Northwest Guizhou Province. However, it is unclear whether the metabolite in D. nobile is influenced by the planting altitude. Hence, to reveal the different metabolite in D. nobile cultivated at the altitude of 336 m, 528 m, and 692 m, ultra-high performance liquid chromatography with Q/TOF-MS couple with multivariate analysis were developed. Using the orthogonal partial least squares-discriminant analysis, 19 different metabolites were discovered and then tentatively assigned their structures as alkaloids and glycosides by comparing mass spectrometry data with in-house database and literature. Moreover, the result of semiquantitative analysis showed the content of dendrobine that was belonged to alkaloids significantly increased at the altitude of 692 m, whereas the content of glycosides demonstrated an accumulation trend at the altitude of 528 m. The results could provide valuable information for the optimal clinical drug therapeutics and provide a reference for quality control. 相似文献
92.
In this work, we report a series of cyclophane fluorescent sensors based on acridine combining with imidazolium through ether linkages. X-ray crystal structures demonstrated the self-assembly behavior of these cyclophanes in the solid state driven by hydrogen bond and π–π interactions. Sensors showed excellent selectivity towards Fe3+ in aqueous solution (H2O/CH3CN?=?49:1, v/v) and H2PO4? in acetonitrile solution with notable color change under UV light, evident changes were also noticed in fluorescence spectra. In fluorescence emission, the obvious turn-off was induced by Fe3+ in aqueous solution and the obvious turn-on as well as bathochromic-shift was induced by H2PO4? in acetonitrile solution. 相似文献
93.
Weihong Liang Wenhao Yin Tingzhong Wang Fayang G. Qiu Junling Zhao 《Tetrahedron letters》2018,59(18):1742-1747
A novel method for the stereoselective conjugate addition of 3-substituted oxindoles to in situ generated o-QMs was described. This process was catalyzed efficiently by a cinchonidine-derived squaramide catalyst in oil-water phase, furnishing the corresponding 3,3-disubsituted oxindole derivatives in moderate to high yields (up to 98%) with high stereoselectivities (up to 95%?ee, 15.4:1?dr). The utility of this reaction was also investigated by the gram-scale synthesis and derivatization of one of the products. 相似文献
94.
Pingping Li Jian Sun Xiaohe Xu Zhisheng Mi Yuyan Lin Jingya Cheng Renren Bai Yuanyuan Xie 《Tetrahedron letters》2018,59(27):2640-2643
A ferric nitrate-promoted cross-dehydrogenative coupling reaction of N-hydroxyphthalimide (NHPI) with toluene derivatives is reported. The reaction proceeded smoothly using molecular oxygen as an oxidant, providing an efficient method for the synthesis of N-hydroxyimide esters. Furthermore, a plausible mechanism was proposed. 相似文献
95.
Yong-Jia Hao Xiao-Si Hu Jin-Sheng Yu Feng Zhou Ying Zhou Jian Zhou 《Tetrahedron》2018,74(52):7395-7398
Reported here is a highly efficient 1,6-conjugate addition of fluorinated silyl enol ethers to para-quinone methides, allowing facile access to a range of β,β-diaryl α-fluorinated ketones with good to high yields. Fe(OTf)3 was identified as the optimal catalyst, with the loading of 3?mol%. Notably, this represent the first 1,6-conjugate addition with fluorinated silyl enol ethers. The synthetic potential of the resulting adducts is also demonstrated. 相似文献
96.
结合2015-2016年新情况,概述近期高分子学科新动态,给出年度基金申请指南,指出基金申请中存在的一些问题. 相似文献
97.
Hower JC Suárez-Ruiz I Mastalerz M Cook AC 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,67(5):1433-1437
A recent paper by Sun [X. Sun, Spectrochim. Acta A 62 (1-3) (2005) 557] attempts to characterize a variety of liptinite, termed "barkinite", from Chinese Permian coals. The component identified does not appear to fundamentally differ from previously-described liptinite macerals included in the International Committee for Coal and Organic Petrology's system of maceral nomenclature. Further, chemical comparisons made with macerals from coals of different rank and age are flawed because the author did not account for changes in chemistry with rank or for the chemical changes associated with botanical changes through geologic time. The author has not satisfactorily proved his hypothesis that the component differs morphologically or chemically from known liptinite-group macerals. 相似文献
98.
化学计量学在我国的发展 总被引:6,自引:0,他引:6
评述了化学计量学在我国近年来的发展,包括多元校正与分辨、稳健方法、化学模式识别、化学定量构效关系、分子模拟与优化、化学专家系统与库主要分支,其中特别对近年来得到飞速发展的新技术如高维数据解析方法,人工神经网络、小波变换给出了较详细的介绍。 相似文献
99.
100.
Yi ZHOU 《数学年刊B辑(英文版)》2022,43(4):499-508
Let u(t, x) be the solution to the Cauchy problem of a scalar conservation law in one space dimension. It is well known that even for smooth initial data the solution can become discontinuous in finite time and global entropy weak solution can best lie in the space of bounded total variations. It is impossible that the solutions belong to, for example, H1 because by Sobolev embedding theorem H1 functions are H¨older continuous. However, the author notes that from any point (t, x), he can draw a generalized characteristic downward which meets the initial axis at y = α(t, x). If he regards u as a function of (t, y), it indeed belongs to H1 as a function of y if the initial data belongs to H1 . He may call this generalized persistence (of high regularity) of the entropy weak solutions.The main purpose of this paper is to prove some kinds of generalized persistence (of high regularity) for the scalar and 2 × 2 Temple system of hyperbolic conservation laws in one space dimension. 相似文献