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991.
B. Leela Maheswara Rao Shaik Nowshuddin Anjali Jha Murali K. Divi M. N. A. Rao 《合成通讯》2017,47(22):2127-2132
A new reagent, tert-butyl (2,4-dioxo-3-azaspiro [5,5] undecan-3-yl) carbonate (Boc-OASUD) for the preparation of N-Boc-amino acids is described. The Boc-OASUD reacts with amino acids and their esters at room temperature in the presence of a base and gives N-Boc-amino acids and their esters in good yields and purity. Introduction of the Boc group takes place without racemization. The Boc-OASUD, being a solid and more stable, is a better alternative to di-tert-butyl dicarbonate which is low melting and has to be dispensed in plastic containers than glass because of its poor stability. 相似文献
992.
Shengqiang Wang Hongtao Lu Jingya Li Dapeng Zou Yusheng Wu Yangjie Wu 《Tetrahedron letters》2017,58(12):1107-1111
An efficient and general protocol for the decarboxylative cross-coupling of pyridazine-3-carboxylic acids with aryl-bromides has been described. This method provides a new avenue for the synthesis of 3-arylpyridazines via decarboxylative cross-coupling strategy by employing the dual-catalyst system of Pd(PPh3)4/Cu2O in the presence of Li2CO3 at 160 °C in DMA. 相似文献
993.
Rupom Borah Eramoni Saikia Sankar Jyoti Bora Bolin Chetia 《Tetrahedron letters》2017,58(12):1211-1215
A green and facile novel procedure has been developed for the synthesis of Cu2O nanoparticles within a very short reaction time using banana pulp extract as a reducing agent. The synthesized nanoparticles are well characterized by SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) and powder XRD (X-ray Diffraction) methods. An environmental benign and highly efficient protocol for the ipso-hydroxylation of aryl and hetero arylboronic acids using bio-fabricated Cu2O nanoparticles as a catalyst and aqueous H2O2 as an oxidant has also been developed. The main advantages of this protocol are the base free reaction condition, reusable and heterogeneous catalytic system, and short reaction time with excellent yields. 相似文献
994.
Önder Özcan İsmail İnci Yavuz Selim Aşçı 《Journal of Dispersion Science and Technology》2017,38(1):65-69
Oxalic acid adsorption from aqueous solution is studied in this work. Multi-walled carbon nanotubes (MWCNT) were used as an adsorbent. The investigated adsorption variables are equilibrium time, initial acid concentration, and temperature. The experimental results were presented using equilibrium isotherm and kinetic models. The used equilibrium models are Langmuir, Freundlich, and Temkin adsorption isotherms. And the kinetic models are Elovich, Lagergren pseudo-first-order and pseudo-second-order kinetic models. The thermodynamics studies were carried out at three different temperatures: 278, 298, and 318 K. Langmuir isotherm was the best fitted equilibrium model for the experimental data. The all applied kinetic models fitted the data suitably. 相似文献
995.
996.
建立了柱前衍生-气相色谱-电子捕获(GC-ECD)法同时测定水中PFBA、PFPeA、PFHxA、PFHpA,PFOA,PFNA,PFDA,PFUnA及PFDoA等(全称见正文)9种全氟羧酸(Perfluorinated carboxylic acids,PFCAs).使用2,4-二氟苯胺(2,4-Difluoroaniline,2,4-DFA)为衍生剂,N,N'-二环己基碳二亚胺(N,N'-Dicy-clohexylcarbodiimide,DCC)为脱水剂,与PFCAs形成酰胺衍生产物,衍生产物通过TR-5毛细管色谱柱分离,并以ECD检测器进行检测.对全氟羧酸衍生化过程中2,4-DFA和DCC用量、衍生反应溶剂、反应温度、反应时间等条件进行了优化,得出最佳衍生化条件.结果表明,在最优实验条件下,9种PFCAs衍生产物的线性相关系数>0.99,检出限为0.62~ 1.38 μg/L,相对标准偏差RSD为1.3%~7.5%.应用本方法对城市污水中全氟类羧酸进行了分析,城市污水中存在以PFPeA、PFHpA和PFOA为主的痕量PFCAs化合物,实际样品的加标回收率在84.4% ~ 120.9%之间.本方法稳定、可靠、成本低,能够满足水样中多种全氟羧酸的同时检测的要求,可为水体中全氟化合物的污染评价提供技术支持. 相似文献
997.
《应用有机金属化学》2017,31(2)
A set of pentacoordinated dimethyltin(IV) complexes of flexible N‐protected amino acids and fluorinated β‐diketone/β‐diketones was screened for their antibacterial activity against Pseudomonas aeruginosa , Staphylococcus aureus and Streptomyces griseus . These pentacoordinated complexes of the type Me2SnAB (where : R = CH(CH3)C2H5, A1H; CH2CH(CH3)2, A2H; CH(CH3)2, A3H; CH2C6H5, A4H; and BH = R'C(O)CH2C(O)R″: R′ = C6H5, R″ = CF3, B1H; R′ = R″ = CH3, B2H; R′ = C6H5, R″ = CH3, B3H; R′ = R″ = C6H5, B4H) were generated by the reactions of dimethyltin(IV) dichloride with sodium salts of flexible N‐protected amino acids (ANa) and fluorinated β‐diketone/β‐diketones (BNa) in 1:1:1 molar ratio in refluxing dry benzene solution. Plausible structures of these complexes were elucidated on the basis of physicochemical and spectral studies. 119Sn NMR spectral data revealed the presence of pentacoordinated tin centres in these dimethyltin(IV) complexes. 相似文献
998.
<正>A high-performance capillary electrophoresis with amperometric detection(CE-AD) method has been developed for the analysis of seven bioactive ingredients,namely ferulic acid(FA),vanillin,vanillic acid,p-hydroxybenzoic acid,caffeic acid,gallic acid and protocatechuic acid,in Rhizoma Chuanxiong.The effects of several factors such as the acidity and concentration of running buffer,the separation voltage,the applied potential to working electrode and the injection time were investigated.Under the optimum conditions,the seven analytes could be well separated within 21 min at the separation voltage of 16 kV in a 60 mmol/L borax running buffer(pH 8.7).A 300μm diameter carbon disk electrode has a good response at potential of +950 mV(vs.SCE) for all analytes.Good linear relationship was established over three orders of magnitude with detection limits(S/N = 3) ranged from 3.3×10~(-7) to 6.7×10~(-9)g/mL.This proposed method has been successfully applied for the determination and comparison of different batches of Rhizoma Chuanxiong samples based on their characteristic electrochemical profiles. 相似文献
999.
橡胶及橡胶制品中4种酚类防霉剂的高效液相色谱法测定 总被引:1,自引:0,他引:1
建立了橡胶及其制品中硝基苯酚(PNP)、2,3,5,6-四氯苯酚(TeCP)、五氯苯酚(PCP)、邻苯基苯酚(OPP)4种酚类防腐剂的高效液相色谱测定方法。样品冷冻粉碎后,经甲醇超声提取,在Venusil-XBP C18色谱柱(250 mm×4.6 mm,5μm)上以10 mmol/L醋酸铵和甲醇为流动相梯度洗脱,采用二极管阵列检测器,PCP、TeCP、OPP的检测波长为220 nm,PNP的检测波长为320 nm。4种酚类防霉剂的质量浓度在0.5~250mg/L范围内与峰面积呈良好的线性关系,相关系数大于0.999 4。丁苯橡胶、硅橡胶基体的加标回收实验结果表明:TeCP、PCP、OPP、PNP在不同基质中的平均加标回收率分别为82%~95%、68%~90%、85%~98%、87%~98%,相对标准偏差小于5%。 相似文献
1000.
研究了朱砂对大鼠脑组织中氨基酸类神经递质含量的影响.将32只Wistar大鼠随机分为低、中、高剂量组和对照组,朱砂灌胃给药14天后,采用高效液相色谱法测定大鼠脑组织中谷氨酸(Glu)、天门冬氨酸(Asp)、甘氨酸(Gly)、γ-氨基丁酸(GABA)和牛磺酸(Tau)的含量,并计算兴奋毒性指数(EI)的变化.与对照组相比较,脑组织中氨基酸类神经递质含量均呈下降趋势,其中Asp和Gly的中、高剂量组差异有统计学意义(P0.05),Tau和GABA的高剂量组有统计学差异(P0.05),Glu和EI所有剂量组均有统计学差异(P0.05).朱砂对氨基酸类神经递质具有一定的抑制作用. 相似文献