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A convenient and chromatography-free 4-step synthesis of analytically pure maslinic acid (1, 41.2%) from oleanolic acid has been developed. Slight variations in the final steps gave an excellent yield of isomeric augustic acid (7, 71.9%). 相似文献
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采用在线扫集-胶束毛细管电动色谱法(sweeping-MEKC)分离测定扛板归中的阿魏酸、咖啡酸和原儿茶酸。采用未涂层熔融石英毛细管(50 cm×50μm,有效柱长36 cm);环境温度25℃;缓冲体系为20 mmol/L NaH2PO4-80mmol/L十二烷基磺酸钠(SDS)-12.5%乙腈(V/V)(pH 2.20),紫外检测波长为216 nm,运行分离电压-20 kV,进样时间100 s。在优化条件下,3种有机酸均在20 min内出峰,峰面积RSD均小于5%。检出限分别达到98.52,118.73和27.27μg/L。 相似文献
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The effect of cationic (cetylpyridinium bromide and cetylpyridinium chloride) anionic (sodium dodecyl sulfate and lithium
dodecyl sulfate) and non-ionic (Brij-35 and Triton-X-100) micelles on the acid-catalyzed hydrolysis of N-phenylbenzohydroxamic
acid in 20 vol.% dioxane medium has been investigated. The kinetic results are explained by both pseudo-phase and Piszkiewicz
cooperativity models. 相似文献
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A new stereoselective total synthesis of malyngic acid has been achieved from a known oxazolidinone derivative via eight steps involving the Evans asymmetric alkylation as the chirality-inducing step and chelation-controlled Zn(BH4)2 reduction of an α-hydroxy ketone intermediate for the installation of the 12,13-anti stereochemistry. Fulgidic acid, the C12-epimer of malyngic acid, has also been synthesized in eight steps from the same starting material by using syn-selective K-Selectride reduction of an α-alkoxy ketone intermediate. 相似文献
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Toyoji Kakuchi Minako Shibata Shigeyuki Matsunami Takeshi Nakato Masayuki Tomida 《Journal of polymer science. Part A, Polymer chemistry》1997,35(2):285-289
The polycondensation of L -aspartic acid ( ASP ) with 6-aminocaproic acid ( ACA ) using o-phosphoric acid produced poly(succinimide-co-6-aminocaproic acid). The yield of the MeOH-insoluble copolymer decreased from 99 to 52% and that of the MeOH-soluble one increased from 9 to 47%, with increasing molar ratio of ACA in the monomer feed. The compositions of the succinimide ( SCI ) unit in the MeOH -insoluble and -soluble copolymers tended to be higher than those of ASP in the monomer feed. The copolymers with the 35 mol % SCI units or above were soluble in DMSO , DMF , and conc- H2SO4 , but those with the 20 and 21 mol % SCI units were soluble only in conc-H2SO4. The melting temperature appeared for the copolymers with less than 76 mol % SCI units. Poly(succinimide-co-6-aminocaproic acid) was easily hydrolyzed to yield poly(aspartic acid-co-6-aminocaproic acid), and it exhibited biodegradability toward activated sludge. © 1997 John Wiley & Sons, Inc. 相似文献
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Mikhail L. Strokin Marina G. Sergeeva Alevtina T. Mevkh 《Applied biochemistry and biotechnology》2000,88(1-3):195-200
The role of serum fatty acid binding proteins (FABPs) in arachidonic acid (AA) uptake by murine peritoneal macrophages has
been studied. The kinetics of [3H]arachidonic acid uptake by the cells was investigated over a wide range of AA concentration (10−10–10−5
M). It was shown that these putative fatty acid transporters dramatically change the uptake processes. In the presence of FABPs,
the time-course curves of AA uptake exhibited two distinct periods: one with a rapid AA uptake during the first hour with
an equilibrium in 1–2.5 h and another with an equilibrium reached in 20 h, whereas in the absence of FABPs the uptake curves
were smooth without kinks and with the equilibrium reached in 10 h. In addition, it was shown that the amount of incorporated
AA was linearly dependent on the concentration of AA over the range of 10−10–10−6
M in the presence of serum FABPs and 10−10–10−7
M in their absence.
We assume that the changes in the character of AA uptake by macrophages in the presence of FABP soccur due to the interaction
of FABPs with the cell plasma membrane. 相似文献
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A rapid, high resolution, and low sample consumption CZE method is developed for peptide nucleic acid (PNA) analysis for the first time. 30% v/v acetonitrile in PNA sample and 20% v/v acetonitrile in 50 mM borax‐boric acid (pH 8.7) as BGE were employed after optimization. The calibration curves were linear for PNA concentration ranging from 1 to 50 μmol/L. LOD and LOQ of PNA were 0.2 and 1.0 μmol/L, respectively. Since the commercially available reagent gives rise to huge PNA peak and an apparent impurity peak, the purity of PNA was evaluated to be about 81.4% by CZE method, obviously lower than the supplier's purity value of 99.9% evaluated by RP–HPLC, and also lower than 94.8% determined with RP–HPLC by our research group. The CZE method takes only 5 min, needs only 90 nL PNA, much less than 20 min and 20 μL PNA in RP–HPLC method. Moreover, the CZE method is applicable for the analysis of glutamic acid modified and lysine modified PNAs, they show different migration time with their corresponding complementary PNAs. Our results show CZE provides a new choice for PNA and modified PNA analysis, also their purity or quality evaluation. 相似文献
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《Green Chemistry Letters and Reviews》2013,6(3):181-187
Abstract Silica-supported acid catalysts were synthesized and characterized for composition, morphology, particle size distribution, and crystallinity. The catalysts are used for the esterification of long-chain aliphatic acids with alcohol to produce the corresponding ester. Process parameters such as time, temperature, and solvent ratio influence the conversion of fatty acid to ester. A supported catalyst was found to show higher catalytic activity as compared to the conventional sulfuric acid catalyst. 相似文献
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Fluoride removal from water by lime materials is a promising defluoridation process. Acid enhanced limestone defluoridation (AELD) technique involves precipitation of CaF2 as well as adsorption of fluoride on the surface of limestone which is capable of reducing fluoride concentration to below the WHO guideline value of 1.5 mg/L. Acids such as acetic acid and citric acid are added to the fluoride water before filtration through limestone column to enhance the Ca2+ activity in solution for precipitation of fluoride as CaF2. This paper describes the effects of these acids on the quality of the limestone during the AELD process, which has been studied to evaluate the reusability of the limestone. The reaction products that formed during the AELD process have also been analyzed. The detail study of the morphology of the limestone before and after use have been done using various analytical techniques, viz., X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy combined with energy dispersive X-ray spectroscopy. The study reveals that the limestone degrades to some extent in the process due to dissolution of calcium carbonate by the acids and adsorption of fluoride by the limestone. While appreciable quantity of the citrate salt of calcium was formed in the column, the acetate salt mostly remained dissolved in the water. Since mainly the surface of the limestone particles take part in the reaction, the limestone particles can be reused for the defluoridation process after cleaning the outer surface. The limestone after use remains also suitable as raw material for cement. 相似文献
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通过乳酸催化脱水制备丙烯酸具有良好的应用前景。为了对其中的催化过程进行有效、及时的监控,建立了一种同时测定乳酸及丙烯酸的阴离子交换色谱法(AEC)。选择Metrohm A Supp 5阴离子交换柱(150 mm×4.0 mm),以2 mmol/L Na2CO3+2 mmol/L NaHCO3混合水溶液为流动相,采用化学抑制电导检测技术,乳酸和丙烯酸在6 min内即可实现完全分离。乳酸和丙烯酸工作曲线的线性范围分别为0.1~500 mg/L和0.1~200 mg/L,检出限分别为0.030 mg/L和0.035 mg/L,加标回收率分别为100.7%~106%和99.6%~103%,相对标准偏差分别为2.16%~2.49%和2.42%~2.48%。该方法准确、快速、灵敏、重现性好。 相似文献
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Dinitroterephthalic acid(DNTPA) and diaminoterephthalic acid(DATPA) were prepared in 85%and 75%yields,respectively. These compounds were characterized by using FTIR and ~1HNMR.DATPA can be used as a monomer for the preparation of polyesters and polyamides. 相似文献
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Johnathan E. Holladay Todd A. Werpy Danielle S. Muzatko 《Applied biochemistry and biotechnology》2004,115(1-3):857-869
Technology to convert biomass into chemical building blocks provides an opportunity to displace fossil fuels and increase
the economic viability of biorefineries. Coupling fermentation capability with aqueous-phase catalysis provides novel routes
to monomers and chemicals, including those not accessible from petrochemical routes. Glutamic acid provides a platform to
numerous compounds through thermochemical approaches including hydrogenation, cyclization, decarboxylation, and deamination.
Hydrogenation of amino acids also provides access to chiral compounds with high enantiopurity. This article detals aqueous-phase
hydrogenation reactions that we have developed that lead to valuable chemical intermediates from glutamic acid. In addition,
13C nuclear magnetic resonance and matrix-assisted laser desorption ionization mass spectral data are presented that provide
a mechanistic picture of the reactions. The results show that hydrogenation of glutamic acid has unique characteristics from
other amino acids and that paradigms in the literature do not hold up for this transformation. 相似文献
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高效液相色谱法分离和测定酒石酸和马来酸 总被引:6,自引:0,他引:6
1引言 酒石酸(2,3一二羟基丁二酸)和马来酸(顺丁烯二酸)都是重要的有机化工原料,它们被广泛地应用于有机合成和其它化工生产领域[1]. 酒石酸的制备常用钨酸作为催化剂,由马来酸识水溶液与过氧化氢进行环氧化反应再经水解精制而成,其中常含有微量的没有反应的马来酸,因此,建立有效的分离和测定酒石酸和马来酸的方法,对于酒石酸生产条件的选择与控制,以及产品的质量检测等都有十分重要的意义. 目前尚未发现有关同时分离和测定酒石酸和马来酸的文献报道.我们首次采用反相高效液相色谱法,跟踪监测了酒石酸生产过程中的物… 相似文献
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Manju Arora Vandna Luthra Ramadhar Singh S. K. Gupta 《Applied biochemistry and biotechnology》2001,96(1-3):173-181
Vibrational spectra of insulator emeraldine base (EB) form of polyaniline and electrical conductive sulfuric acid-and phosphoric
acid-doped emeraldine salts (ES) were studied in the region of 4000-400 cm−1 at ambient temperature by Fourier transform infrared spectroscopy. Infrared transmittance spectra of EB and ES were investigated
to understand the bonding behavior of different organic and inorganic groups present in the polymeric chains and their structural
variations on protonation by sulfate or phosphate ion inclusion in the polymer salt network. These studies revealed the para-coupling
of deformed disubstituted benzenoid (B) and quinoid (Q) rings with ends capped predominantly by (B4Q1) units. The deformation
of B and Q rings was confirmed by the appearance of many weak bands, very weak bands, and satellite structures in strong transmittance
peaks of polymeric chain-constituting groups. Protonation takes place at the nitrogen sites of Q rings and forms semiquinone
radical ions in ES. The vibrational bands pertaining to B rings, Q rings, B4Q1 units, semiquinone segment, sulfate ions, and
phosphate ions were observed and assigned from these measurements. The shift in peak position of some bands with gain or loss
in intensity and appearance of some new bands were observed in sulfuric acid-and phosphoric acid-doped ES spectra. These variations
are attributed to the formation of new structural groups in ES on protonation and a change in crystalline field by sulfate
and phosphate ion doping for crosslinking the polymeric chains. 相似文献
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胶束扫集毛细管电泳分离测定绿原酸和咖啡酸 总被引:1,自引:0,他引:1
采用胶束扫集毛细管电泳分离测定双黄连口服液中的绿原酸和咖啡酸.试验条件为:重力进样时间40 s;以20 mmol/L NaH_2PO_4,100 mmol/L 十二烷基磺酸钠(SDS)为电泳缓冲液(含体积分数15%甲醇,pH 2.20),分离电压-20 kV,检测波长214 nm,讨论了pH、SDS浓度、样品溶剂等对分离效果的影响.在优化条件下,绿原酸和咖啡酸的检出限分别达到1.02和0.168 μg/mL,线性范围分别为5.86~51.5 μg/mL和1.27~14.5 μg/mL. 相似文献