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Baskaran Durairaj - - 2007
Grafting reactions of living polystyryllithium (PSLi) with acid chloride containing multi-walled carbon nanotubes (MWNTs-COCI) were performed under vacuum in benzene at room temperature. Covalent grafting of polystyrene (PS) was characterized using spectroscopic, microscopic, and thermogravimetric analyses. Grafting at different ratios of macroanion to acylchloride of the carbon nanotubes showed that ...
Jeong Gwi-Taek - - 2007
Fatty acid methyl esters, also referred to as biodiesel, have been determined to have a great deal of potential as substitutes for petro-diesel. In order to optimize conversion yield in the biodiesel production process, feedstocks were previously recommended to be anhydrous, with a free fatty acid content of less than ...
Solbach C - - 2007
The preparation of [11C]chloroform by direct chlorination of [11C]methane using gaseous chlorine by variation of temperature and reaction time (inert gas flow) without catalyst support for the online production of [11C]diazomethane in a flow-through synthesis apparatus is described in this work. At an oven temperature of 400 degrees C and ...
Chang Jee-Gong - - 2007
The kinetics and mechanisms for the unimolecular decomposition reactions of formic acid and oxalic acid have been studied computationally by the high-level G2M(CC1) method and microcanonical RRKM theory. There are two reaction pathways in the decomposition of formic acid: The dehydration process starting from the Z conformer is found to ...
Gannon Michael K MK - - 2007
Deprotonation and lithium-bromine exchange in 5- or 3-bromothiophene-2-carboxylic acids with t-BuLi form the corresponding dianion, which reacts highly regioselectively in the presence of 0.25 equiv of tetramethyl-1,2-ethylenediamine with 3,6-bis(dimethylamino) chalcogenoxanthones to give S- and Se-containing rhodamines. Quenching studies with D2O indicate that an extra equivalent of t-BuLi is not necessary ...
Iijima Ryosuke - - 2007
In a previous report, we had demonstrated the antioxidant activity of the sialic acid N-acetylneuraminic acid (Neu5Ac, NANA). This activity can counteract the cytotoxicity of hydrogen peroxide (H2O2), and the antitoxicity is a result of a direct chemical reaction, whereby NANA reduces H2O2 in the culture media. The influence of ...
Florea-Wang Diana - - 2007
Phenylacetic acid mustard (PAM; 2), a major metabolite of the anticancer agent chlorambucil (CLB; 1), was allowed to react with 2'-deoxyadenosine (dA), 2'-deoxyguanosine (dG), 2'-deoxycytidine (dC), 2'-deoxy-5-methylcytidine (dMeC), and thymidine (T) at physiological pH (cacodylic acid, 50% base). The reactions were followed by HPLC and analyzed by HPLC/MS and/or (1)H-NMR ...
Yuan Hushan H Center for Molecular Imaging Research, Massachusetts General Hospital and Harvard Medical School, 149 13th Street, Charlestown, MA 02129, - - 2007
Wortmannin (Wm), a steroid-like molecule of 428.4 Da, appears to be unstable in biological fluids (apparent chemical instability), yet it exhibits an antiproliferative activity in assays employing a 48 hr incubation period (prolonged bioactivity), a situation we refer to as the "wortmannin paradox." Under physiological conditions, Wm covalently reacts with ...
Zhang Jinli - - 2008
Both conventional heating and ultrasound effect on the cyclopalladated ferrocenylimines catalyzed Suzuki reaction of phenylboronic acid with a range of arylhalides in neat water was investigated. Heterogenous reaction of electron-withdrawing arylchlorides with phenylboronic acid could also result in good yields by using Cat. 2. It was found that the ultrasonic ...
Fu Yuchuan - - 2007
Dimethoxymethane was synthesized from the direct oxidation of methanol with high conversion and selectivity over specially designed bifunctional V(2)O(5)/TiO2 catalysts with redox and enhanced acidic character, in which the surface acidity played an essential role for inhibiting the formation of formaldehyde through the enhanced condensation reaction of formaldehyde with methanol ...
Mojarrad Javid S - - 2007
Chitin was prepared from Persian Gulf shrimp (Metapenaeus monoceros), and then, the obtained chitin was hydrolyzed by hydrochloric acid solutions. The production yield of glucosamine hydrochloride from chitin was optimized, and the effect of three factors (acid concentration, acid to chitin ratio, and reaction time) was investigated. A Box-Behnken design ...
Beşe Ayşe Vildan - - 2007
This work presents the optimum conditions of dissolution of copper in copper converter slag in sulphuric acid ferric sulphate mixtures in the presence and absence of ultrasound. The Taguchi method was used to determine the optimum conditions. The parameters investigated were the reaction temperature, acid concentration, ferric sulphate concentration and ...
Rudzevich Yuliya - - 2007
The importance of tetraamino calix[4]arenes as starting materials is distinctly increased by the first versatile protective group for opposite amino functions. Reaction with trityl chloride leads to the 1,3-dialkylated derivative easily isolated in 34% yield; after a first acylation of the remaining amino groups, the trityl residues can be removed ...
Rivera Daniel G - - 2007
A detailed study of the Baeyer-Villiger reaction of 3-ketosteroids has been performed by using m-chloroperoxybenzoic and trifluoroperoxyacetic acids as oxidants. The process was fully regiospecific for 3-keto-5alpha-steroids with the employ of both peracids, and only partially regioselective for 3-keto-5beta-steroids by using trifluoroperoxyacetic acid. Interestingly, the reaction resulted completely unselective for ...
Zhu S - - 2007
Stearic acid and triethanolamine (TEA) in a molar ratio of 2:1 were mixed in aqueous solution at 80 degrees C and subsequently cooled to ambient temperature. The structural evolution of the resultant sample during storage was characterized by using light microscopy, Cryo-SEM, differential scanning calorimetery, pH, infrared spectroscopy, elemental analysis, ...
Mohrig Jerry R - - 2007
As part of a comprehensive investigation of electronic effects on the stereochemistry of base-catalyzed 1,2-elimination reactions, we observed a new syn intramolecular pathway in the elimination of acetic acid from beta-acetoxy esters and thioesters. 1H and 2H NMR investigation of reactions using stereospecifically labeled tert-butyl (2R*,3R*)-3-acetoxy-2,3-2H2-butanoate (1) and its (2R*,3S*) ...
Hariharan Mahesh - - 2007
[reaction: see text] A novel donor-acceptor conjugate 1 was synthesized, and its interactions with various amino acids have been investigated as compared to the model system 2. The conjugate 1 unusually forms an intramolecular charge-transfer complex in the aqueous medium and undergoes selective binding interactions with tryptophan. The uniqueness of ...
Hung Hui-Ming - - 2007
The heterogeneous reactions of oleic acid (OL) and oleic-acid/sodium-chloride(aq) (OL/NaCl(aq)) mixture droplets with ozone are studied at two relative humidities (RH). The reactions were monitored concomitantly using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT-IR) for the organic species and UV-vis spectrometry for the ozone concentration in order to investigate ...
Sato Masaru - - 2007
D-alanine-D-alanine ligase from Thermotoga maritima ATCC 43589 (TmDdl) was a useful biocatalyst for synthesizing D-amino acid dipeptides. TmDdl showed a broad substrate specificity at a high temperature; however, ATP was required for its reaction. One of the methods for an effective ATP supply was the coupling reaction with an ATP ...
Sanz Roberto - - 2007
Simple Brønsted acids such as p-toluenesulfonic acid monohydrate (PTS) efficiently catalyze a direct substitution of the hydroxyl group in propargylic alcohols with 1,3-dicarbonyl compounds. Selective propargylation or allenylation is obtained depending on the nature of the alkynol. Reactions can be performed in air in undried solvents with water being the ...
Wang Jun - - 2007
Research to the racemization reaction of L-amino acids is performed through a laboratory-made 16-channel capillary array electrophoresis. The impact factors such as catalyst, solvent, and reactive time which influenced the racemization reaction are screened, the experimental results proved that the capillary array electrophoresis is qualified as combinatorial enantiomeric screening system.
Nakamura Satoshi - - 2007
In this paper, we deal with the scope and mechanism of the strong Brønsted acid-catalyzed intramolecular cyclization reaction of methyl 3-aryl-2-nitropropionates to give 4H-1,2-benzoxazines. This reaction can be regarded as an oxygen functionalization of the aromatic ring wherein the oxygen atom is derived from the nitro group in the molecule, ...
Liu Haitao - - 2007
The molecular mechanism of precursor evolution in the synthesis of colloidal group II-VI semiconductor nanocrystals was studied using 1H, 13C, and 31P NMR spectroscopy and mass spectrometry. Tri-n-butylphosphine chalcogenides (TBPE; E = S, Se, Te) react with an oleic acid complex of cadmium or zinc (M-OA; M = Zn, Cd) ...
Barder Timothy E - - 2007
[reaction: see text] Although boronic acids are widely used in metal-catalyzed reactions, it is difficult to assay their consumption. As such, we developed a reversible fluorescent sensor that is activated upon binding a boronic acid. The sensor can be used to monitor consumption of a boronic acid in Suzuki-Miyaura reactions. ...
Avirah Rekha R - - 2007
[reaction: see text] A novel chemosensor based on semisquaraine dye (SSQ) for selective detection of Hg2+ is described. SSQ is obtained in quantitative yields from the reaction between squaric acid and 6-ethoxy-2-quinaldinium iodide. SSQ in combination with surfactant shows a dual chromogenic and fluorogenic response selectively toward Hg2+ as compared ...
Sumitomo K - - 2007
Reactions of 3-methyl-1-phenyl-2-pyrazoline-5-one (MCI-186) with hypochlorous acid and superoxide were analysed by spectrophotometry and mass spectrometry. The results were applied to the neutrophil system to evaluate the scavenging activity of neutrophil-derived active oxygen species by MCI-186. MCI-186 reacted rapidly with hypochlorous acid (1 x 10(6) M(-1)s(-1)) to form a chlorinated ...
Einbu Aslak - - 2007
The monosaccharide 2-amino-2-deoxy-D-glucose (glucosamine, GlcN) has recently drawn much attention in relation to its use to treat or prevent osteoarthritis in humans. Glucosamine is prepared from chitin, a process that is performed in concentrated acid, such as hydrochloric acid. This process involves two acid-catalyzed processes, that is, the hydrolysis of ...
Kasashima Yoshio - - 2007
Intramolecular cyclization of 3-hydroxy acids was investigated using iodine as a catalyst under solvent-free conditions. The reaction proceeded to completion in the heterogeneous system. Lactones were obtained by intramolecular cyclization of 3-hydroxy acids. Propella lactone (11-oxatricyclo[4.4.3.0(1,6)]tridecan-12-one) was conveniently synthesized from 3-hydroxy acid ((6-hydroxyspiro[4.5]dec-6-yl)acetic acid) in 88% yield with carbon skeleton ...
Isidro-Llobet Albert - - 2007
A double side-reaction, consisting in the formation of Fmoc-beta-Ala-OH and Fmoc-beta-Ala-AA-OH, during the preparation of Fmoc protected amino acids (Fmoc-AA-OH) with Fmoc-OSu is discussed. Furthermore, the new Fmoc-2-MBT reagent is proposed for avoiding these side-reactions as well as the formation of the Fmoc-dipeptides (Fmoc-AA-AA-OH) and even tripeptides, which is another ...
Jabbari Arash - - 2006
[Structure: see text] Density functional theory studies of the hetero-Cope reactions of 4-nitroso-1-butenes and nitrosobicyclo[2.2.2]hexenes are reported. The reactions proceed via concerted mechanisms. The electron-withdrawing methoxycarbonyl group alpha- to the nitroso group decreases the activation barrier. Lewis acids such as SbF5 and TiCl4 accelerate the reactions, as has been found ...
Major Dan Thomas - - 2006
Combined quantum mechanical/molecular mechanical simulations have been carried out to investigate the origin of the carbon acidity enhancement in the alanine racemization reaction catalyzed by alanine racemase (AlaR). The present study shows that the enhancement of carbon acidity of alpha-amino acids by the cofactor pyridoxal 5'-phosphate (PLP) with an unusual, ...
Taylan N - - 2007
Colemanite is one of the most important boron minerals used for production of boric acid. Boric acid (H(3)BO(3)) is produced by the reaction of colemanite (2CaO.3B(2)O(3).5H(2)O) with sulfuric acid in a heterogeneous solid-liquid reaction leading to crystallization of gypsum as a byproduct. The influence of ultrasound on the dissolution of ...
Kakkar Rita - - 2007
The conformational preferences of thiohydroxamic acids (N-hydroxythioamides) are investigated by the density functional B3LYP/6-311++G(3df,3pd)//B3LYP/6-31G(d) method in this work. Unlike hydroxamic acids, the thione and thiol forms are found to be equally stable in the gas phase, and the reaction pathways for the interconversion between the thione and thiol forms have ...
Chang Chun - - 2007
Studies were carried out on the effects of temperature, acid concentration, liquid:solid ratio and reaction time on levulinic acid production from wheat straw using response surface methodology. The P-value of the coefficient for acid concentration was 0.0002, suggesting that this was highly significant. The quadratic effects of temperature and liquid:solid ...
Chen Y-X - - 2006
We present and discuss the results of an in situ IR study on the mechanism and kinetics of formic acid oxidation on a Pt film/Si electrode, performed in an attenuated total reflection (ATR) flow cell configuration under controlled mass transport conditions, which specifically aimed at elucidating the role of the ...
Rigout Muriel L A - - 2006
Fourier transform infrared (FT-IR) spectroscopy has been successfully employed to follow the formation of phthalic anhydride and 1,8-naphthalic anhydride on heating their corresponding acids. The effects of three heterocumulenes, cyanamide, dicyandiamide, and sodium cyanate, on the temperature of formation of the anhydrides were also investigated using this method. It was ...
Schaefer William H - - 2006
Glucuronidation is an important mechanism used by mammalian systems to clear and eliminate both endogenous and foreign chemicals. Many functional groups are susceptible to conjugation with glucuronic acid, including hydroxyls, phenols, carboxyls, activated carbons, thiols, amines, and selenium. Primary and secondary amines can also react with carbon dioxide (CO(2)) via ...
Hegedüs Laszló - - 2006
In the present mechanistic schemes of the ferroin-catalyzed oscillatory Belousov-Zhabotinsky (BZ) reaction the oxidation of the organic substrates (bromomalonic or malonic acid) by ferriin (the oxidized form of the catalyst) plays an important role. As the organic products of these reactions were not yet identified experimentally, they were studied here ...
Yavari Issa - - 2007
The reaction between alkyl isocyanides and isopropylidene Meldrum's acid in the presence of 1,2-ethanediol leads to N (1)-(alkyl)-2-(5,7-dioxo-1,4-dioxepane-6-yl)-2-methylpropanamides. 1,3-Propanediol or 1,4-butanediol produce hydroxyalkyl 1-(tert-butyl)-4,4-dimethyl-2,5-dioxo-3-pyrrolidinecarboxylates. When the reaction was performed in the presence of catechol, bis(2-hydroxyphenyl) 2-[2-(tert-butylamino)-1,1-dimethyl-2-oxoethyl]malonate was obtained. 2-Aminophenols react with alkyl isocyanides in the presence of isopropylidene Meldrum's acid ...
Vikbjerg Anders Falk - - 2007
Acyl modification of the sn-2 position in phospholipids (PLs) was conducted by acidolysis reaction using immobilized phospholipase A(2) (PLA(2)) as the catalyst. In the first stage we screened different carriers for their ability to immobilize PLA(2). Several carriers were able to fix the enzyme and maintain catalytic activity; however, the ...
Cacciapaglia Roberta - - 2006
Important insight has been obtained into the mechanism of the reversible acid-catalysed transacetalation of cyclophane formaldehyde acetals (formals) C(i) in CDCl(3), at 25 degrees C. The order of appearance of the lowest oligomers in the early stages of the equilibration reaction is fully consistent with ring-fusion/ring-fission processes in which oxonium ...
Mattinen Maija-Liisa - - 2006
Laccase-catalyzed oligomerization of proteins was studied using Trametes hirsuta laccase (ThL) and coactosin as a model system. The reaction mechanism was elucidated using free amino acids and the tripeptide Gly-Leu-Tyr as substrates. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and high-performance liquid chromatography (HPLC) as well as oxygen consumption ...
Zhang Wei-Guo - - 2006
Several ionic liquids were used as reaction media for penicillin G acylase catalysis. In all the assayed ionic liquids, [bmim]PF6 proved good media for PGA-catalyzed hydrolysis. A novel [bmim]PF6/water two-phase system is provided for 6-aminopenicillanic acid (APA) production, which will be more benefical than aquous batch systems used widely in ...
Dömling Alexander - - 2006
Arrays of amino-acid-derived isocyanoamides are conveniently produced on a multigram scale in one step by the solventless aminolysis of the corresponding methyl esters with primary or secondary aliphatic amines. Most of the corresponding isocyanides precipitate during the reaction and can be filtered to yield highly pure, colorless, and odorless solids. ...
Reynolds J C - - 2006
The products arising from the ozonolysis of oleic acid (cis-9-octadecenoic acid) in solution have been studied using negative ion mode electrospray ionization ion trap mass spectrometry. Oleic acid is an important component of atmospheric organic aerosol and is a key model species in predicting aerosol physical and chemical characteristics. The ...
Adediran S A SA Department of Chemistry, Wesleyan University, Middletown, Connecticut 06459, - - 2006
Beta-lactam antibiotics restrict bacterial growth by inhibiting DD-peptidases. These enzymes catalyze the final transpeptidation step in bacterial cell wall biosynthesis. Although much structural information is now available for these enzymes, the mechanism of the actual transpeptidation reaction has not been studied in detail. The reaction is known to involve a ...
He Zhiqiao - - 2007
Decolorization of the azo dye C.I. Reactive Black 5 (RB5) in solution by a combination of sonolysis and ozonation was investigated. The results showed that the optimum pH for the reaction was 11.0, and both lower and higher pH decreased the decolorization rate. Increasing the initial concentration of RB5 led ...
Liao Wei - - 2007
The objectives of this study were to statistically study the effects of reaction conditions of temperature, acid concentration, and reaction time on manure components of cellulose, hemicellulose, lignin, and nitrogen during dilute acid treatment of dairy manure; and to further optimize the accumulation of cellulose for later enzymatic conversion to ...
Lin Weimin - - 2006
A zinc-mediated chain extension reaction is the key step in the preparation of gamma-keto amides derived from amino acids. The use of tandem reaction sequences, in which the intermediate zinc enolate is trapped with electrophilic reagents, results in the incorporation of alpha-substituents, which mimic the side chains found in natural ...
Hong Wen-Xu - - 2006
[reaction: see text] An efficient total synthesis of (2S,2'S,3aR,3'aR,8aR,8'aR)-6,6'-dichloro-3a,3'a-dihydroxy-1,1',2,2',3,3a,3',3'a,8,8a,8',8'a-dodecahydro-5,5'-bipyrrolo[2,3-b]indole-2,2'-dicarboxylic acid, the central amino acid component of chloptosin (1), is described. Starting from m-chloronitrobenzene, this C(2)-symmetrical amino acid was synthesized by using a 14-step route, in which a Zinin benzidine rearrangement, intramolecular Heck reaction, and selenocyclization and oxidative deselenation served as ...
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