- Dioxygen reactivity of iron(ii)-gentisate/1,4-dihydroxy-2-naphthoate complexes of N4 ligands: Oxidative coupling of 1,4-dihydroxy-2-naphthoate
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The influence of supporting ligands and co-ligands on the dioxygen reactivity of a series of iron(ii) complexes, [(6-Me3-TPA)FeII(GN-H)]+ (1), [(6-Me3-TPA)FeII(DHN-H)]+ (1a), [(BPMEN)FeII(GN-H)]+ (2), [(BPMEN)FeII(DHN-H)]+ (2a), [(TBimA)FeII(GN-H)]+ (3), and [(TBimA)FeII(DHN-H)]+ (3a) (GN-H2 = 2,5-dihydroxybenzoic acid and DHN-H2 = 1,4-dihydroxy-2-naphthoic acid) of N4 ligands, is presented. The iron(ii)-gentisate complexes react with dioxygen to afford the corresponding iron(iii) species. On the contrary, DHN-H undergoes oxidative C-C coupling to form [2,2′-binaphthalene]-1,1′,4,4′-tetrone 3-hydroxy-3′-carboxylic acid (BNTHC) on 1a, and [2,2′-binaphthalene]-1,1′,4,4′-tetrone 3,3′-dicarboxylic acid (BNTD) on 2a and 3a. In each case, the reaction proceeds through an iron(iii)-DHN species. The X-ray single crystal structures of [(6-Me3-TPA)FeII(BNTD)] (1Ox) and [(BPMEN)FeII(BNTD)] (2Ox) confirm the coupling of two DHN-H molecules. The formation of iron(iii) product without any coupling of co-ligand from the complexes, [(BPMEN)FeII(HNA)]+ (2b) and [(BPMEN)FeII(5-OMeSA)]+ (2c) (HNA = 1-hydroxy-2-naphthoate, 5-OMeSA = 5-methoxysalicylate) confirms the importance of para-hydroxy group for the coupling reaction. The unusual coupling of DHN-H by the iron(ii) complexes of the neutral N4 ligands is distinctly different from the oxygenolytic aromatic C-C cleavage of DHN by the iron(ii) complex of a facial N3 ligand.
- Rahaman, Rubina,Munshi, Sandip,Banerjee, Sridhar,Chakraborty, Biswarup,Bhunia, Sarmistha,Paine, Tapan Kanti
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Read Online
- Formation of oxygen radicals in solutions of different 7,8- dihydropterins: Quantitative structure-activity relationships
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Under certain conditions, 7,8-dihydroneopterin in aqueous solution promotes hydroxyl-radical formation. Thus, we investigated the stimulation of hydroxyl-radical formation by ten different 7,8-dihydropterins (=2-amino-7,8- dihydropteridin-4(1H)-one), i.e., 6-(1'-hydroxy) derivatives 1 and 2, methyl derivatives 3-7, and 6-(1'-oxo) derivatives 8-10. All but the 6-(1'-oxo) derivatives produced hydroxyl radicals, as measured by the amount of salicylic acid hydroxylation products. This amount was dependent on the stability of the dihydropterin used. In the presence of chelated iron ions, hydroxylation was increased in every case; even 6-(1'-oxo) derivatives showed a low hydroxylation of salicylic acid. The degree of increase, however, strongly depended on the side chain of the dihydropterin. The 7,8- dihydroneopterin (2) was investigated in more detail. Iron ions influenced both, the stability of 2 and hydroxyl-radical formation. While iron ions determined the kinetics of the reaction, the amount of 2 was responsible for the amount of hydroxyl radicals formed. Our data establish that promotion of hydroxyl-radical formation by 7,8-dihydropterins depends on the oxidizability of the dihydropterins and on their iron-chelating properties.
- Oettl, Karl,Pfleiderer, Wolfgang,Reibnegger, Gilbert
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Read Online
- A chlorogenic acid esterase from a metagenomic library with unique substrate specificity and its application in caffeic and ferulic acid production from agricultural byproducts
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Soil microbes are an abundant source of enzymes with unique properties that may be useful for industrial applications. As most wild-type strains show low chlorogenic acid esterase expression and activity, and most microbes cannot be cultured in the laboratory, a metagenomic approach provides methods of identifying new enzymes. In this study, a gene encoding a chlorogenic acid esterase, named Tan410, was isolated from a soil metagenomic library and overexpressed in Escherichia coli BL21 (DE3). The recombinant enzyme, with a predicted molecular weight of 54.88 kDa, was purified to homogeneity. The K m and V max values for Tan410 were 1.26 mM and 0.33 mM min–1, respectively, with chlorogenic acid as the substrate. Its optimum temperature and pH for reaction were 30 °C and 7.5, respectively. The enzyme exhibited moderate thermostability and broad pH stability (3.0–10.0). Tan410 was also able to hydrolyse ethyl ferulate, methyl caffeate, propyl gallate, ethyl gallate, methyl vanillate, methyl benzoate, ethyl benzoate, methyl 2,5-dihydroxybenzoate, and methyl 3,5-dihydroxybenzoate, and it released caffeic and ferulic acids from agricultural byproducts (destarched wheat bran and coffee pulp). Tan140 has potential for industrial application in biomass valorization.
- Gui, Lun,Long, Qizhang,Yao, Jian
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- Black TiO2 nanotube arrays decorated with Ag nanoparticles for enhanced visible-light photocatalytic oxidation of salicylic acid
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Novel forms of black TiO2 nanotubes-based photocatalysts for water purification were prepared. Two features were combined: decoration of TiO2 nanotube arrays with Ag nanoparticles (sample TiO2-NT's@Ag) and further hydrogenation of this material (TiO2-NT's@Ag-HA). Obtained photocatalysts show high efficiency for degradation of salicylic acid, a typical water-borne pollutant. The photocatalysts considerably exceed the photocatalytic properties of TiO2 nanotubes and commercial TiO2 P25 taken as a reference for modeling of the photocatalytic process. The comparison of photocatalytic activities between novel photocatalyst was based on a numerical approach supported by the complex kinetic model. This model allowed a separate study of different contributions on overall degradation rate. The contributions include: salicylic acid photolysis, photocatalysis in UVB, UVA and in the visible part of applied simulated solar irradiation. The superior photocatalytic performance of the photocatalyst TiO2-NT's@Ag-HA, particularly under visible irradiation, was explained by the combined effect of a local surface plasmon resonance (LSPR) due to Ag nanoparticles and creation of additional energy levels in band-gap of TiO2 due to Ti3+ states at nanotube surfaces. The presence of Ag also positively influence charge separation of created electron-holes pairs. The synergy of several effects was quantified by a complex kinetic model through the factor of synergy, fSyn. Stability testing indicated that the catalysts were stable for at least 20 h. The novel design of catalysts, attached on Ti foils, presents a solid base for the development of more efficient photocatalytic reactors for large-scale with a long-term activity.
- Plodinec, Milivoj,Gr?i?, Ivana,Willinger, Marc G.,Hammud, Adnan,Huang, Xing,Pan?i?, Ivana,Gajovi?, Andreja
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p. 883 - 896
(2018/11/10)
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- Evidence for the electrochemical production of persulfate at TiO2 nanotubes decorated with PbO2
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It is well known that PbO2-based electrodes are considered to be non-active anodes, producing higher concentrations of hydroxyl radicals in aqueous solutions, and consequently, favouring the electrochemical degradation of organic pollutants. However, no evidence has been reported on the production of persulfates using this kind of electrode in sulphate aqueous solutions. For this reason, the aim of this work is to prepare (by an electrochemical procedure (anodization and electrodeposition)) and characterize (by X-ray diffraction, scanning electron microscopy, and potentiodynamic measurements) Ti/TiO2-nanotubes/PbO2 disk electrodes (with a geometrical area of 65 cm2) in order to evaluate the electrochemical production of persulfate using Na2SO4 solution as the support electrolyte and applying current densities of 7.5 and 60 mA cm-2, as well as the influence of the electrosynthesis of hydroxyl radicals, in concomitance. The results clearly showed that significant production of hydroxyl radicals and persulfate is achieved at the Ti/TiO2-nanotubes/PbO2 surface, but this depends on the current density. The production of OH at the Ti/TiO2-nanotubes/PbO2 surface in Na2SO4 solution was confirmed by a RNO spin trapping reaction. The results were compared with those of a Ti/Pt electrode in order to understand the effect when a lower amount of OH is produced at the active anode surface. Based on the results, the Ti/TiO2-nanotubes/PbO2 anode could exhibit good electrocatalytic properties for environmental applications involving persulfate oxidants.
- Santos, José Eudes L.,Antonio Quiroz, Marco,Cerro-Lopez, Monica,De Moura, Dayanne Chianca,Martínez-Huitle, Carlos A.
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p. 5523 - 5531
(2018/04/02)
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- HPLC study on Fenton-reaction initiated oxidation of salicylic acid. Biological relevance of the reaction in intestinal biotransformation of salicylic acid
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Fenton-reaction initiated in vitro oxidation and in vivo oxidative biotransformation of salicylic acid was investigated by HPLC-UV-Vis method. By means of the developed high performance liquid chromatography (HPLC) method salicylic acid, catechol, and all the possible monohydroxylated derivatives of salicylic acid can be separated. Fenton oxidations were performed in acidic medium (pH 3.0) with two reagent molar ratios: (1) salicylic acid: iron: hydrogen peroxide 1:3:1 and (2) 1:0.3:1. The incubation samples were analysed at different time points of the reactions. The biological effect of elevated reactive oxygen species concentration on the intestinal metabolism of salicylic acid was investigated by an experimental diabetic rat model. HPLC-MS analysis of the in vitro samples revealed presence of 2,3- and 2,5-dihydroxybenzoic acids. The results give evidence for nonenzyme catalysed intestinal hydroxylation of xenobiotics.
- Nyúl, Eszter,Kuzma, Mónika,Mayer, Mátyás,Lakatos, Sándor,Almási, Attila,Perjési, Pál
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p. 1040 - 1051
(2018/10/24)
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- Complete Enzymatic Oxidation of Methanol to Carbon Dioxide: Towards More Eco-Efficient Regeneration Systems for Reduced Nicotinamide Cofactors
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A novel system for in situ regeneration of reduced nicotinamide cofactors (NADH) is proposed: through a cascade of alcohol dehydrogenase (ADH), formaldehyde dismutase (FDM) and formate dehydrogenase (FDH) complete oxidation of methanol to carbon dioxide (CO2) is coupled to the regeneration of NADH. As a consequence, from one equivalent of methanol three equivalents of NADH can be obtained. The feasibility of this cascade is demonstrated at the examples of an NADH-dependent reduction of conjugated C=C-double bonds (catalysed by an enoate reductase) and the NADH-dependent hydroxylation of phenols (catalysed by a monooxygenase). The major limitation of the current regeneration system is the comparably poor catalytic efficiency of the methanol oxidation step (low kcat and high KM value of the ADH used) necessitating higher than theoretical methanol concentrations.
- Kara, Selin,Schrittwieser, Joerg H.,Gargiulo, Serena,Ni, Yan,Yanase, Hideshi,Opperman, Diederik J.,Van Berkel, Willem J. H.,Hollmann, Frank
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supporting information
p. 1687 - 1691
(2015/06/02)
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- Aromatic hydroxylation of salicylic acid and aspirin by human cytochromes P450
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Aspirin (acetylsalicylic acid) is a well-known and widely-used analgesic. It is rapidly deacetylated to salicylic acid, which forms two hippuric acids - salicyluric acid and gentisuric acid - and two glucuronides. The oxidation of aspirin and salicylic acid has been reported with human liver microsomes, but data on individual cytochromes P450 involved in oxidation is lacking. In this study we monitored oxidation of these compounds by human liver microsomes and cytochrome P450 (P450) using UPLC with fluorescence detection. Microsomal oxidation of salicylic acid was much faster than aspirin. The two oxidation products were 2,5-dihydroxybenzoic acid (gentisic acid, documented by its UV and mass spectrum) and 2,3-dihydroxybenzoic acid. Formation of neither product was inhibited by desferrioxamine, suggesting a lack of contribution of oxygen radicals under these conditions. Although more liphophilic, aspirin was oxidized less efficiently, primarily to the 2,5-dihydroxy product. Recombinant human P450s 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4 all catalyzed the 5-hydroxylation of salicylic acid. Inhibitor studies with human liver microsomes indicated that all six of the previously mentioned P450s could contribute to both the 5- and 3-hydroxylation of salicylic acid and that P450s 2A6 and 2B6 have contributions to 5-hydroxylation. Inhibitor studies indicated that the major human P450 involved in both 3- and 5-hydroxylation of salicylic acid is P450 2E1.
- Boji?, Mirza,Sedgeman, Carl A.,Nagy, Leslie D.,Guengerich, F. Peter
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- Effect of oxidants on photoelectrocatalytic decolourization using α-Fe2O3/TiO2/activated charcoal plate nanocomposite under visible light
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The present study is to investigate the effect of oxidants H2O2, S2O82-, BrO3-, ClO3- and IO4- with different concentrations on photoelectrocatalytic decolourization of Lanasol yellow 4G (LY4G) as a model contaminant using α-Fe2O3/TiO2/activated charcoal plate (ACP) nanocomposite under visible light. In this system, the decolourization efficiency increased with increasing BrO3-, ClO3- and IO4- doses but reached an optimum amount with H2O2 and S2O82- at 1 mM. Experimental data revealed that the decolourization rate of LY4G in all of the processes obeyed pseudo-first-order kinetics. Total organic carbon (TOC) results indicated that 21% and 100% of organic substrate were mineralized respectively after 80 min and 8 h. The gas chromatography-mass spectrometry (GC-MS) analysis was employed to identify the intermediate products. Also, a plausible degradation pathway was proposed. Finally, the real wastewater treatment was investigated by chemical oxygen demand (COD) measurements. This journal is
- Ayoubi-Feiz, Baharak,Aber, Soheil,Sheydaei, Mohsen
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p. 19368 - 19378
(2015/04/14)
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- General method for the synthesis of salicylic acids from phenols through palladium-catalyzed silanol-directed C-H carboxylation
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A silanol-directed, palladium-catalyzed C-H carboxylation reaction of phenols to give salicylic acids has been developed. This method features high efficiency and selectivity, and excellent functional-group tolerance. The generality of this method was demonstrated by the carboxylation of estrone and by the synthesis of an unsymmetrically o,o′-disubstituted phenolic compound through two sequential C-H functionalization processes.
- Wang, Yang,Gevorgyan, Vladimir
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p. 2255 - 2259
(2015/02/19)
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- Regioselective ortho-carboxylation of phenols catalyzed by benzoic acid decarboxylases: A biocatalytic equivalent to the Kolbe-Schmitt reaction
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The enzyme catalyzed carboxylation of electron-rich phenol derivatives employing recombinant benzoic acid decarboxylases at the expense of bicarbonate as CO2 source is reported. In contrast to the classic Kolbe-Schmitt reaction, the biocatalytic equivalent proceeded in a highly regioselective fashion exclusively at the ortho-position of the phenolic directing group in up to 80% conversion. Several enzymes were identified, which displayed a remarkably broad substrate scope encompassing alkyl, alkoxy, halo and amino- functionalities. Based on the crystal structure and molecular docking simulations, a mechanistic proposal for 2,6-dihydroxybenzoic acid decarboxylase is presented.
- Wuensch, Christiane,Gross, Johannes,Steinkellner, Georg,Lyskowski, Andrzej,Gruber, Karl,Glueck, Silvia M.,Faber, Kurt
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p. 9673 - 9679
(2014/03/21)
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- Inclusion complex containing epoxy resin composition for semiconductor encapsulation
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The invention is an epoxy resin composition for sealing a semiconductor, including (A) an epoxy resin and (B) a clathrate complex. The clathrate complex is one of (b1) an aromatic carboxylic acid compound, and (b2) at least one imidazole compound represented by formula (II): wherein R2 represents a hydrogen atom, C1-C10 alkyl group, phenyl group, benzyl group or cyanoethyl group, and R3 to R5 represent a hydrogen atom, nitro group, halogen atom, C1-C20 alkyl group, phenyl group, benzyl group, hydroxymethyl group or C1-C20 acyl group. The composition has improved storage stability, retains flowability when sealing, and achieves an effective curing rate applicable for sealing delicate semiconductors.
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- Hydroxyl Radicals quantification by UV spectrophotometry
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Hydroxilation of aromatic compounds is an oxidative process that has been employed as indirect method to quantify the produced hydroxyl radicals during an advanced oxidation process (a-OH). This is usually complicated by the radical high reactivity and short life time and therefore a scavenging agent such as salicylic acid is commonly employed. This usually implies a rather sophisticated analytical method such as chromatography. In this work, however, a relatively simple and low cost method is proposed to achieve the aforementioned objective. This method is based on UV-Vis spectrophotometry and was employed to quantify the hydroxyl radicals produced during the electrochemical oxidation of water when employing a platinum anode in a galvanostatic type process. Salicylic acid was employed as a-OH scavenger. The concentration of the hydroxilated resulting products, 2,3-dihidroxybenzoic Acid and 2,5-dihydroxibenzoic Acid, was determined by UV-Vis Spectroscopy and utilized to quantify the hydroxyl radicals. In addition, mineralization was followed by Chemical Oxygen Demmand measurements.
- Peralta,Roa,Hernandez-Servin,Romero,Balderas,Natividad
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p. 137 - 141
(2014/04/03)
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- More efficient redox biocatalysis by utilising 1,4-butanediol as a 'smart cosubstrate'
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1,4-Butanediol is shown to be an efficient cosubstrate to promote NAD(P)H-dependent redox biocatalysis. The thermodynamically and kinetically inert lactone coproduct makes the regeneration reaction irreversible. Thereby not only the molar surplus of cosubstrate is dramatically reduced but also faster reaction rates are obtained.
- Kara, Selin,Spickermann, Dominik,Schrittwieser, Joerg H.,Leggewie, Christian,Van Berkel, Willem J. H.,Arends, Isabel W. C. E.,Hollmann, Frank
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p. 330 - 335
(2013/03/29)
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- PROCESS FOR PREPARING 2,5-DIHYDROXYTEREPHTHALIC ACID
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The present invention provides a process for preparing 2,5-dihydroxyterephthalic acid which comprises reacting a dialkali metal salt of hydroquinone with carbon dioxide in a reaction medium in the presence of a potassium salt represented by formula (I): [in-line-formulae]CnH2n+1COOK??(I)[/in-line-formulae] wherein n is an integer of 1-17. According to the process for preparing 2,5-dihydroxyterephthalic acid of the present invention, 2,5-dihydroxyterephthalic acid can be produced both safely and at a low cost under industrially advantageous conditions. Further, the process according to the present invention causes less damage to reaction equipment and the like.
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Page/Page column 3
(2012/12/14)
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- Functional annotation and characterization of 3-hydroxybenzoate 6-hydroxylase from Rhodococcus jostii RHA1
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The genome of Rhodococcus jostii RHA1 contains an unusually large number of oxygenase encoding genes. Many of these genes have yet an unknown function, implying that a notable part of the biochemical and catabolic biodiversity of this Gram-positive soil actinomycete is still elusive. Here we present a multiple sequence alignment and phylogenetic analysis of putative R. jostii RHA1 flavoprotein hydroxylases. Out of 18 candidate sequences, three hydroxylases are absent in other available Rhodococcus genomes. In addition, we report the biochemical characterization of 3-hydroxybenzoate 6-hydroxylase (3HB6H), a gentisate-producing enzyme originally mis-annotated as salicylate hydroxylase. R. jostii RHA1 3HB6H expressed in Escherichia coli is a homodimer with each 47 kDa subunit containing a non-covalently bound FAD cofactor. The enzyme has a pH optimum around pH 8.3 and prefers NADH as external electron donor. 3HB6H is active with a series of 3-hydroxybenzoate analogues, bearing substituents in ortho- or meta-position of the aromatic ring. Gentisate, the physiological product, is a non-substrate effector of 3HB6H. This compound is not hydroxylated but strongly stimulates the NADH oxidase activity of the enzyme.
- Montersino, Stefania,Van Berkel, Willem J.H.
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experimental part
p. 433 - 442
(2012/07/14)
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- Application of advanced oxidation processes for removing salicylic acid from synthetic wastewaters
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In this study, advanced oxidation processes (AOPs) such as anodic oxidation (AO), UV/H2O2 and Fenton processes (FP) were investigated for the degradation of salicylic acid (SA) in lab-scale experiments. Boron-doped diamond (BDD) film electrodes using Ta as substrates were employed for AO of SA. In the case of FP and UV/H2O2, most favorable experimental conditions were determined for each process and these were used for comparing with AO process. The study showed that the FP was the most effective process under acidic conditions, leading to the highest rate of SA degradation in a very short time interval. However, the results showed that Ta/BDD films had high electrocatalytic activity for complete degradation of SA; even if it employs more time for complete elimination of the SA respect to FP. Additionally, AO led to a sixfold acceleration of the oxidation rate compared with the UV/H2O2 process. Finally a rough comparison of the specific energy consumption shows that AO process reduced the energy consumption by at least 90% compared with the UV/H2O2 process.
- Chen, Xue Ming,da Silva, Djalma Ribeiro,Martínez-Huitle, Carlos A.
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experimental part
p. 101 - 104
(2010/11/17)
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- Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes
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The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was studied by differential pulse voltammetry over a wide pH range. The hydrolysis products were 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA.
- Enache, Teodor Adrian,Fatibello-Filho, Orlando,Oliveira-Brett, Ana Maria
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scheme or table
p. 569 - 577
(2010/12/25)
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- Process for the synthesis of hydroxy aromatic acids
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Hydroxy aromatic acids are produced in high yields and high purity (>95%) from halogenated aromatic acids in a reaction mixture containing a copper source and a ligand that coordinates to copper.
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Page/Page column 20-21
(2008/06/13)
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- Aluminium(III) adsorption: A soft and simple method to prevent TiO 2 deactivation during salicylic acid photodegradation
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Deposition of poisoning species on TiO2 during salicylic acid photodegradation can be halted when Al(III) has been previously adsorbed on the catalyst surface; this widens the application of photocatalysis to more concentrated solutions. The Royal Society of Chemistry 2005.
- Franch, Maria Isabel,Peral, Jose,Domenech, Xavier,Ayllon, Jose A.
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p. 1851 - 1853
(2007/10/03)
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- Selective ortho-cleavage of methoxymethyl- and 4-methoxybenzyl ethers
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Iodine in methanol has been found to be an effective catalyst system for the cleavage of alkoxymethyl ethers. This catalyst system is particularly useful for the selective removal of ortho-methoxymethyl- and ortho-(4-methoxybenzyl) ethers in the presence
- Keith, John M.
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p. 2739 - 2742
(2007/10/03)
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- Demethoxylation and hydroxylation of methoxy- and hydroxybenzoic acids by OH-radicals. Processes of potential importance for food irradiation
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The hydroxylation process for methoxy- and hydroxy-benzoic acids (MBA, HBA) induced by γ-radiation is compared. 2-, 3-, and 4-methoxybenzoic acid as well as 3-hydroxybenzoic acid have been irradiated in N2O and aerated solutions up to 1.5 kGy. The products were analyzed by HPLC. The results for 2- and 4-HBA have been taken from literature data. The OH·-adduct distribution is generally the same for the hydroxy- as well as for the methoxy-benzoic acid isomers. With both 4-HBA and 4-MBA more than 65% C3-adducts and about 15% C4-adducts are formed, which could be proved by their reactions with K3 Fe(CN)6. Oxidation of the nonipso-adducts of 3-HBA and 3-MBA results in 84 and 87% of the corresponding phenols. Whereas in N2O-saturated solutions only part of the OH·-radicals leads to substrate decomposition, in the presence of air, the degradation of both kinds of compounds is equivalent to [OH·]. The nonipso OH·-adducts of the HBAs are converted into 68-77% hydroxylation products. With the MBAs, the hydroxylation process is ≤10%. This is attributed to different decay pathways of the peroxyl radicals, intermediates formed by O2 addition to the OH·-adducts. The hydroxyperoxycyclohexadienyl radicals of the HBAs decay mainly by HO2· elimination to the corresponding phenols, those of the MBAs decay predominantly by fragmentation of the benzene ring, yielding to nonidentified aliphatic products. The replacement of -OCH3 by -OH is practically not influenced by the presence of oxygen, it increases in the sequence 3-MBA 4-MBA 2-MBA. For 2-MBA, yields of more than 15% are obtained. Both processes, hydroxylation as well as demethoxylation, might be of importance for the recognition of radiolytical changes in foodstuff.
- Gaisberger,Solar
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p. 394 - 404
(2007/10/03)
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- Pathway of anthracene modification under simulated solar radiation
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Exposure of polycyclic aromatic hydrocarbons (PAHs) to sunlight results in rapid structural photomodification generally via oxidation reactions. These PAH modification products are in many cases more toxic than their parent compounds. In this study, anthracene (ANT), a rapidly photooxidized PAH, was irradiated with simulated solar radiation (SSR, 100 μmol m-2 s- 1) in aqueous solution to examine the photomodification pathway. The photoproducts formed were identified by HPLC. The ANT product profile after 9 h in SSR was very complex, with more than 20 compounds detected. The photoproducts formed were anthraquinones, benzoic acids, benzaldehydes and phenols showing the process to be oxidative in nature. Some of the anthraquinones were themselves subject to photooxidation, and were thus intermediates in the product pathway. The kinetics of ANT photooxidation revealed a pseudo first-order reaction with a half-life of 2 h under the SSR source used. The kinetics of product formation allowed deduction of a probable photomodification pathway. This study indicates that PAH photooxidation products are likely to exist as complex, dynamically changing mixtures in PAH contaminated aquatic environments.
- Mallakin, Ali,George Dixon,Greenberg, Bruce M.
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p. 1435 - 1441
(2007/10/03)
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- Unusual phenolic glycosides from Cotoneaster orbicularis
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The whole plant of Cotoneaster orbicularis contains the novel di-C- glycosylflavone, 4'',4'''-di-O-β-glucopyranosyl-vicenin II, or 6,8-di-C-β- Cellobiosylapigenin, as well as the hitherto unknown natural phenolic glucoside, gentisic acid 2-O-β-glucopyranoside, or orbicularin. Further phenolics are protocatechuic, anisic, caffeic, p-coumaric acids, catechin, epicatechin, 2''-O-α-rhamnopyranosylvitexin, vitexin, rutin, isoquercetrin, hyperin and naringenin. All structures were determined by routine methods of analysis and confirmed mostly by 1H- and 13C-NMR. (C) 2000 Elsevier Science Ltd.
- El-Mousallamy, Amani M.D.,Hussein, Sahar A.M.,Merfort, Irmgard,Nawwar, Mahmoud A.M.
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p. 699 - 704
(2007/10/03)
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- Crystalline cepham acid addition salts and processes for their preparation
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Novel crystalline cephem acid addition salts and processes for their preparation Compounds of the formula I STR1 in which n is equal to 1 or 2 and m is 0.4-2.6, and where X is the anion of a carboxylic acid, have antibacterial activity.
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- COMPOSITIONS AND METHODS FOR THE TREATMENT OF IMMUNOMEDIATED INFLAMMATORY DISORDERS
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Compositions and methods for the prevention and treatment of immunomediated inflammatory disorders, especially for those disorders associated with the respiratory tract, are provided. More particularly, a tryptase inhibitor, typically a hydroxyaroyl or hydroxyheteroaroyl substituted dipeptide, is administered. Also provided by this invention are pharmaceutical compositions, typically aerosol or topical, as well as aerosol devices for administering these compositions intranasally.
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- Photochemical hydroxylation of salicylic acid with hydrogen peroxide; mechanistic study of substrate sensitized reaction
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The photochemical hydroxylation of salicylic acid (SA) by hydrogen peroxide proceeds via the same intermediate independently of the excited reactant (i.e. SA or H2O2). This conclusion is supported by the similar effect of pH on the quantum yields and on the isomer ratio of formed products: 2,3-dihydroxybenzoic acid (2,3-DHB) and 2,5-dihydroxybenzoic acid (2,5-DHB). The product ratio ([2,3-DHB]/[2,5-DHB]) is not affected by H2O2 concentration.
- Lang, Kamil,Brodilova, Jirina,Lunak, Stanislav
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p. 1729 - 1737
(2007/10/03)
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- Hydroxybenzoic acids from Boreava orientalis
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A new guaiacylglycerol ether, threo-guaiacylglycerol-8'-vanillic acid ether, pyrocatechuic acid, pyrocatechuic acid 3-O-β-D-glucoside, gentisic acid, gentisic acid 5-O-β-D-glucoside, vanillic acid and vanillic acid 4-O-β-D-glucoside were identified from fruits of Boreava orientalis.Structural elucidation was carried out on the basis of UV, mass, 1H and 13C NMR spectral data, including 2D shift-correlation and selective INEPT experiments.
- Sakushima, Akiyo,Coskun, Maksut,Maoka, Takashi
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p. 257 - 262
(2007/10/02)
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- Hydroxylation by Electrochemically Generated OH. Radicals. Mono- and Polyhydroxylation of Benzoic Acid: Products and Isomers' Distribution
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The electrochemical Fenton reaction (simultaneous reduction of dioxygen and ferric ions) permits a controlled production of OH. radicals.These are used for the stepwise hydroxylation of benzoic acid to mono- and polyhydroxylated products.The quantitative distribution of all the hydroxylated products is achieved by use of HPLC.The overall reaction scheme is established and the rate constants of the individual steps are measured.
- Oturan, Mehmet A.,Pinson, Jean
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p. 13948 - 13954
(2007/10/02)
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- The Photoinduced Fenton Reaction; Mechanism of Photosensitized Catalyst Generation
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Laser flash-photolytic studies along with determination of the hydroxylation kinetics of salicylic acid under continuous irradiation (λirr = 589 nm) have shown that the active species inducing the photoreduction of Fe(III) salicylate (i.e. the photogeneration of the catalyst) is the excited singlet state of methylene blue, 1MB(+).The hydroxylation products are 2,3- and 2,5-dihydroxybenzoic acid.Binuclear complexes containing iron in various oxidation states (i.e.Fe(II) and Fe(III)) seem to be effective hydroxylation catalysts. - Keywords: Methylene blue / Hydrogen peroxide / Photosensitization / Hydroxylation
- Lang, Kamil,Lunak, Stanislav,Sedlak, Petr,Kubat, Pavel,Brodilova, Jirina
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p. 203 - 210
(2007/10/02)
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- Quantitation of the hydroxyl radical adducts of salicylic acid by micellar electrokinetic capillary chromatography: Oxidizing species formed by a Fenton reaction
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There has been controversy concerning the products formed by a Fenton reaction. We determined the hydroxyl radical (.OH) generated in a Fenton reaction system with no iron chelator using micellar electrokinetic capillary chromatography (MECC). The hydroxyl radical generated in this Fenton system attacked salicylic acid to produce major products of 2,3- and 2,5-dihydroxybenzoic acid (DHB), 2,3-DHB being prominent. Hydroxyl radical scavengers, such as mannitol, ethanol, thiourea and a ferric chelator, Desferal, significantly diminished the peaks for DHBs, showing production of .OH. We compared the MECC method with the electron paramagnetic resonance (EPR) spin trapping technique. The quantity of DHBs obtained by MECC increased dose-dependently up to 1 μM Fe2+ at a fixed concentration of H2O2, whereas that of the spin adduct by EPR showed a bell-shaped curve. This quantitation of .OH adducts by MECC supports the proposal that the oxidizing species formed by a Fenton reaction with no chelator is .OH. The EPR spin trapping method appears to be erroneous, particularly when iron is present at a higher concentration than hydrogen peroxide. The application of this method to the paraquat effect in vitro is demonstrated, and the possibility for analysis of .OH in vivo is also discussed.
- Tomita,Okuyama,Watanabe,Watanabe
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p. 428 - 433
(2007/10/03)
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- PHOTOCHEMICAL HYDROXYLATION OF SALICYLIC ACID DERIVATIVES WITH HYDROGEN PEROXIDE, CATALYZED WITH Fe(III) AND SENSITIZED WITH METHYLENE BLUE
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Substitution of hydrogen in the carboxy or hydroxy group of a salicylic acid molecule with a methyl group, which hinders the coordination of Fe(III), results in a pronounced reduction of photocatalytic effects.The complex of Fe(III) with salicylic acid is the precursor of the thermal catalyst arising on irradiation.
- Lunak, Stanislav,Muzart, Jacques,Brodilova, Jirina
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p. 905 - 912
(2007/10/02)
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- THE ROLE OF HYDROGEN PEROXIDE IN DIOXYGEN INDUCED HYDROXYLATION OF SALICYLIC ACID
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The photochemically initiated oxidation of salicylic acid by molecular oxygen in the presence of 3- leads to a mixture of 2,3- and 2,5-dihydroxybenzoic acids.Iron(II) generated by the photoreduction is reoxidized by dioxygen.Hydrogen peroxide formed in this reaction takes part in the Fenton reaction in the presence of Fe(II).Experiments with OH* radical scavengers document the role of radicals in the photochemical and thermal hydroxylation of salicylic acid.
- Lang, Kamil,Wagnerova, Dana M.,Brodilova, Jirina
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p. 2447 - 2453
(2007/10/02)
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- Polyamines and polypeptides useful as antagonists of excitatory amino acid neuro-transmitters and/or as blockers of calcium channels
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This invention relates to certain polyamines and polypeptides found to be present in the venom of the Agelenopsis aperta spider. The polyamines of this invention and the salts thereof antagonize excitatory amino acid neurotransmitters, which neurotransmitters affect cells of various organisms and are useful in antagonizing said neurotransmitters, per se, in the treatment of excitatory amino acid neurotransmitter mediated diseases and conditions and in the control of invertebrate pests. The polypeptides of this invention and one of said polyamines and the salts thereof block calcium channels in cells of various organisms and are useful in blocking said calcium channels in cells, per se, in the treatment of calcium channel mediated diseases and conditions and in the control of invertebrate pests. This invention also relates to compositions comprising said polyamines, polypeptides and salts thereof.
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- Formation of 2,5-Dihydroxybenzoic acid during the reaction between 1O2 and salicylic acid: Analysis by ESR oximetry and HPLC with electrochemical detection
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The oxygen consumption, vis-a-vis 1O2 production during irradiation of dyes such as rose bengal, merocyanine-540, and aluminum phthalocyaninetetrasulfonate, in the presence of salicylic acid was measured by electron spin resonance (ESR) oximetry. Concomitantly, formation of 2,5-dihydroxybenzoic acid (2,5-DHBA) in the same sample was analyzed by HPLC-EC. Both O2 consumption and 2,5-DHBA formation were stimulated by D2O, quenched by azide, unaffected in the presence of catalase, superoxide dismutase, and hydroxyl radical scavengers (ethanol, formate, etc.), and vastly diminished under N2. The stoichiometry between 1O2 consumption and 2,5-DHBA formation was determined to be ca. 0.5. On the basis of experiments using histidine, the chemical rate constant for the reaction between 1O2 and salicylic acid was determined to be 0.20 × 106 M-1 s-1. Furthermore, 1O2 generated from the thermal decomposition of the water-soluble endoperoxide of 3,3′-(1,4-naphthylidene)dipropionate (NDPO2) was shown to react with salicylic acid to form 2,5-DHBA as the major product. We conclude that exclusive formation of 2,5-DHBA is highly diagnostic of 1O2 intermediacy in photochemical systems and in biochemical systems lacking metabolic activity. HPLC-EC is thus a valuable adjunct to ESR oximetry in the characterization of 1O2 and may, on the basis of the selectivity of this reaction, provide a sensitive analytical method for detecting 1O2 intermediacy.
- Kalyanaraman,Ramanujam, Sujatha,Singh, Ravinder J.,Joseph, Joy,Feix, Jimmy B.
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p. 4007 - 4012
(2007/10/02)
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- VOLATILE CONSTITUENTS OF BALSAM POPLAR: THE PHENOL GLYCOSIDE CONNECTION
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Key Word Index - Populus balsamifera; Salicaceae; balsam poplar; phenol glycosides; 6-hydroxycyclohex-2-enone; cyclohexan-1,2-dione; salicortin; trichocarpin; trichocarpigenin.The volatile metabolites of balsam poplar winter-domant buds are a complex array of mono- and sesquiterpenoids with 1,8-cineol, trans-nerolidol and (+)-(1R,1'R)-α-bisabolol being the major components.On the other hand the volatiles of internodes (stems between buds) consist mainly of salicaldehyde and (+)-6-hydroxycyclohexanone with minor amounts of cyclohexan-1,2-dione and an unidentified compound.This is the first report of these cyclohexanones as natural products; salicortin, a phenol glycoside, appears to be their biosynthetic precursor.A second phenol glycoside, trichocarpin, is present in poplar internodes; and it is the progenitor of trichocarpigenin (benzyl gentisate), an easily formed artifact.
- Mattes, Benjamin R.,Clausen, Thomas P.,Reichardt, Paul B.
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p. 1361 - 1366
(2007/10/02)
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- Quinone derivatives, their production and use
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New quinone derivatives of the formula: STR1 wherein R1 is methyl or methoxy, or two of R1 combine to represent --CH=CH--CH=CH--, R is amino which may be substituted or --OR4 wherein R4 is hydrogen, C1-4 alkyl or --CH2 --CH=C(CH3 --CH2 --m H (wherein m is an integer of 1 to 10), and n is an integer of 1 to 10 when R is amino which may be substituted, or n is an integer of 2 to 10 when R is --OR4, and their hydroquinone forms, have useful physiological activities such as blood-pressure decreasing and antiallergic activities.
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- On the Oxygenation of Several Aromatic and Aliphatic Compounds with Aqueous Ferrous Ion-molecular Oxygen
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Hydroxylation was shown to occur readily in the reactions of aromatic compounds siuch as benzoic acid, nitrobenzene, acetanilide, and phenol with ferrous ion-molecular oxygen in 0.5M phosphate buffer (pH 6.8) at 40 deg C for 3 h.The yields of hydroxylated products were higher than those obtained with other reported hydroxylation systems of transition metal-molecular oxygen.The NIH shift was not observed in the title reactions of C(4)-deuterioacetanilide and C(4)-deuteriobenzoic acid.This system was also demonstrated to oxygenate caproic acid to give a mixture of 3-, 4-, and 5-oxocaproic acids in 67percent total yield. Keywords ---- hydroxylation of aromatic compound; ferrous ion; molecular oxygen; benzoic acid; nitrobenzene; acetanilide; phenol; NIH shift; oxygenation of caproic acid; GC-MS of methyl oxocaproate
- Miura, Toshiaki,Shibata, Kunihiko,Adachi, Kenichi,Sawaya, Takuji,Kimura, Michiya
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p. 100 - 105
(2007/10/02)
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- Trifluoroacetic Acid Catalysed Claisen Rearrangement of 5-Allyloxy-2-hydroxybenzoic Acid and Esters: an Efficient Synthesis of (+/-)-Mellein
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5-Allyloxy-2-hydroxybenzoic acid (1a) and the esters (1b - f) in refluxing trifluoroacetic acid are smoothly converted into 3,4-dihydro-5,8-dihydroxy-3-methylisocoumarin (3) and the corresponding 4-alkoxycarbonyl-2,3-dihydro-5-hydroxy-2-methylbenzofurans (4a - f) via regioselective Claisen rearrangement to the 6-position of the aromatic nucleus with subsequent acid catalysed cyclisation.
- Harwood, Laurence M.
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p. 1120 - 1122
(2007/10/02)
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- STERIC EFFECTS IN THE METALLATION OF ALKOXY- AND DIALKOXY-BENZENES
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With the aim of examining the role of steric factors in determining the position of metallation, the reaction of n-butyllithium with a series of 1,2-dialkoxy-, 1,2-alkylthio-, 1,4-dialkoxy-, and 2-t-butyl-1-alkoxy-benzenes has been studied in the presence and in the absence of N,N,N',N'-tetramethylethylenediamine (TMEDA).Steric factors are particularly relevant in the case of 2-t-butyl-alkoxybenzenes where the yields of metallation dramatically decrease passing from the methoxy to the isopropoxy derivative, while with the t-butoxy derivative only cleavage of the ether bond occurs.
- Bernard, Angela Maria,Piras, Pier Paolo,Plumitallo, Antonio,Melis, Stefana,Sotgiu, Francesca
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p. 443 - 446
(2007/10/02)
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- A Method for the Separation of Benzoic Acids by Cation-excange Chromatography Using the AAA 881 Amino-acid Analyzer
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The authors studied the separation of benzoic acid and its hydroxy derivatives by cation-excange chromatography.The AAA 881 amino-acid analyzer served to fractionate these substances.For this purpose, the amino-acid analyzer was connected with the Specord UV-VIS and the Uvicord II LKB 8300, respectively.M 82 resins, which are used in amino-acid analysis, were employed for separation.The substances were well separated from each other in a short time.Various buffer gradients were used in cation-excange chromatography.Sodium citrate buffers (pH-4.25 and 5.42) were em ployed in separating salicylic acid (o-hydroxybenzoic acid), m-hydroxybenzoic acid and p-hydroxybenzoic acid.A sodium borate buffer (pH=10.2) was utilized in fractionating benzoic acid on M 82 columns.Since dihydroxybenzoic acids may occur in the plant, animal and human organism as salicylic acid metabolites, these acids have been included in the present study. 2,3-Dihydroxybenzoic acid (o-pyrocatechuic acid) and 2,5-dihydroxybenzoic acid (gentisic acid) were separared from the starting material by means of MV 82 columns using a lithium citrate buffer (pH=3.1).The compounds under investigation were in part synthetized by the authors.Coupling of the AAA 881 amino-acid analyzer with the Specord UV-VIS and the Uvicord II LKB 8300 may also be used as a variant of the prefractionaction of animal or plant materials.
- Illig, M.,Graeser, H.
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p. 117 - 120
(2007/10/02)
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