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141.
142.
Chemical investigation on the stem and root of Melicope pteleifolia afforded three new prenylated benzene metabolites as racemic mixtures, named pteleifolins A–C ( 1 – 3 , resp.). Their gross structures were elucidated on the basis of spectroscopic analysis, especially 2D‐NMR experiments. An enantiomer resolution of (±)‐ 1 using chiral HPLC was performed, and the absolute configuration of the enantiomers were determined to be (+)‐(S) 1 and (?)‐(R) 1 by means of circular‐dichroism analysis.  相似文献   
143.
Abstract

An operationally simple domino approach for the ruthenium-catalyzed synthesis of (E)-2,3′-bi(3H-indol)-3-one O-alkyl oximes by the region- and stereoselective three-component, four-molecule reactions of indoles with sodium nitrite and alkyl bromides under mild reaction condition in dimethylformamide is described. Remarkably, multiple bonds including C?C, C=N, and C?O bonds were conveniently formed in one pot. The reaction is tolerant to air and is atom economical, in accordance with the concept of modern green chemistry.  相似文献   
144.
This work demonstrates an efficient way to prepare chiral propargylic alcohols by asymmetric addition of terminal Zn-acetylide to aldehydes catalyzed by bifunctional zinc-based complexes. The corresponding products with moderate to good yields and enantioselectivities were obtained in the absence of moisture-sensitive Ti(O i Pr)4.  相似文献   
145.
The organic/inorganic hybrid nanomaterials containing silica nanoparticles are synthesized by sol-gel crosslinking process. The tetraethoxysilane (TEOS) and γ-aminopropyltriethoxylsilane as coupling agents are used as a precursor. The 2,4,6-tri [(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) as crosslinking agent is used to form covalent bonds among the inorganic nanoparticles. The chemical and morphological structures of the organic/inorganic hybrid are characterized with FTIR spectra, 29Si-NMR, x-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscope (AFM). The results show that the organic/inorganic hybrid forms covalent bond between the inorganic nanoparticle and Tri-EBAC. The network organic/inorganic hybrid can form good film with even nanometer particles. The network organic/inorganic hybrids nanomaterial not only exhibits the thermal properties of inorganic compounds, but also exhibits the thermal properties of organic polymer.  相似文献   
146.
Growth and fermentation characteristics, biomass composition, lipid characterization and metabolic profiling analysis of two different Schizochytrium sp. strains, the original strain and the industrial adaptive strain, were investigated in the fed-batch fermentation process. The final cell biomass, total lipids content, docosahexanoic acid (DHA) content and DHA productivity of the adaptive strain were much higher than those of the original strain. The metabolic distinctions which extensively existed between these two strains were revealed by the score plot of principal component analysis. In addition, potential biomarkers responsible for discriminating different strains were identified as myo-inositol, histidine, alanine, asparagine, cysteine, and oxalic acid. These findings provided new insights into the industrial strain screening and further improvement of DHA production by Schizochytrium sp.  相似文献   
147.
化学感觉包括了红辣椒产生的灼烧感、椒样薄荷产生的清凉感、碳酸饮料产生的麻刺感和葡萄酒产生的涩感,是化学物质刺激到感受冷、热、疼痛等神经系统而产生的敏感性反应。化学感觉是一个相对较新的术语,最早称为共同化学感觉,后来又称为三叉神经反应。化学感觉与嗅觉、味觉相互结合形成一种独特的食品香味,尽管其他感官输入(例如质地、色泽和温度等)也参与整个香味形成过程。本文对化学感觉的基本特征、它与嗅觉、味觉的相互作用及其转导机制进行了概括介绍。  相似文献   
148.
A novel dual-drug delivery system based on mesoporous-macroporous silica/polyelectrolytes-SBA-15 has been synthesized. The structure and composition of these materials were characterized by powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and N2 adsorption–desorption measurements. In this system, water-soluble metformin hydrochloride and fat-soluble ibuprofen were used as model drugs to study the controlled release behavior. The pH-controlled release of individual drugs was obtained by the primary release of metformin hydrochloride from polyelectrolytes-SBA-15 in acid condition and the predominant release of ibuprofen from MMC in alkaline environment. The results show that the polyelectrolytes-SBA-15/mesoporous-macroporous silica can be used as dual-drug release system and the individual drug can be controlled release with the change of pH value of the environment.  相似文献   
149.
A multifunctional system for intracellular drug delivery and simultaneous fluorescent imaging was constructed by using histidine‐tagged, cyan fluorescent protein (CFP)‐capped magnetic mesoporous silica nanoparticles (MMSNs). This protein‐capped multifunctional nanostructure is highly biocompatible and does not affect cell viability or proliferation. The CFP acts not only as a capping agent, but also as a fluorescent imaging agent. The nanoassembly was activated by histidine‐based replacement, leading to release of drug molecules encapsulated in the nanopores into the bulk solution. The fluorescent imaging functionality would allow noninvasive tracking of the nanoparticles in the body. By combining the drug delivery with cell‐imaging capability, these nanoparticles may provide valuable multifunctional nanoplatforms for biomedical applications.  相似文献   
150.
Treatment of germacrone ( 1 ) with different electrophiles, and of its epoxy derivatives germacrone‐4,5‐epoxide ( 2 ), germacrone‐1,10‐epoxide ( 3 ) and isogermacrone‐4,5‐epoxide ( 4 ) with Brönsted/Lewis acids and TiIII, gives rise to a great structural diversity. Thus, by using a maximum of two steps, the production of more than 40 compounds corresponding to 14 skeletons is described. Computational calculations rationalizing the structural divergence produced are also described. Finally, since some of the compounds generated are bioactive natural sesquiterpenes, the mechanisms of formation of these substances will provide new insights in their biosynthesis.  相似文献   
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