- Manganese Porphyrin Catalyzed Homogeneous Aqueous Oxidation of Organic Molecules by Magnesium Monoperoxyphthalate (MMPP)
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Magnesium monoperoxyphthalate (MMPP) oxidizes a variety of organic molecules in neutral homogeneous aqueous solutions at room temperature.A water-soluble porphyrin complex, meso-tetrakis-(4-N-methylpyridyl)porhyrinatomanganese(III) chloride, Mn(III)TMPyP(4) Cl, acts as an efficient catalyst for the epoxidation and hydroxylation of water-soluble hydrocarbons.
- Zheng, Tu-Cai,Richardson, David E.
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- “Dark” Singlet Oxygen Made Easy
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An operationally simple continuous flow generator of “dark” singlet oxygen has been developed. The singlet oxygen was efficiently reacted with several chemical traps to give the corresponding oxygenated products in high yields. The developed “dark” singlet oxygen generator has been successfully applied in the synthesis of the antimalarial drug artemisinin.
- Elsherbini, Mohamed,Allemann, Rudolf K.,Wirth, Thomas
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- Direct monitoring of biocatalytic deacetylation of amino acid substrates by1H NMR reveals fine details of substrate specificity
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Amino acids are key synthetic building blocks that can be prepared in an enantiopure form by biocatalytic methods. We show that thel-selective ornithine deacetylase ArgE catalyses hydrolysis of a wide-range ofN-acyl-amino acid substrates. This activity was revealed by1H NMR spectroscopy that monitored the appearance of the well resolved signal of the acetate product. Furthermore, the assay was used to probe the subtle structural selectivity of the biocatalyst using a substrate that could adopt different rotameric conformations.
- De Cesare, Silvia,McKenna, Catherine A.,Mulholland, Nicholas,Murray, Lorna,Bella, Juraj,Campopiano, Dominic J.
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- Reactive ZrIV and HfIV butterfly peroxides on polyoxometalate surfaces: Bridging the gap between homogeneous and heterogeneous catalysis
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At variance with previously known coordination compounds, the polyoxometalate (POM)-embedded ZrIV and HfIV peroxides with formula: [M2(O2)2(α-XW 11O39)2]12- (M=ZrIV, X=Si (1), Ge (2); M=HfIV, X=Si (3)) and [M6(O 2)6(OH)6(γ-SiW10O 36)3]18- (M=ZrIV (4) or Hf IV (5)) are capable of oxygen transfer to suitable acceptors including sulfides and sulfoxides in water. Combined 1HNMR and electrochemical studies allow monitoring of the reaction under both stoichiometric and catalytic conditions. The reactivity of peroxo-POMs 1-5 is compared on the basis of substrate conversion and kinetic. The results show that the reactivity of POMs 1-3 outperforms that of the trimeric derivatives 4 and 5 by two orders of magnitude. Reversible peroxidation of 1-3 occurs by H 2O2 addition to the spent catalysts, restoring oxidation rates and performance of the pristine system. The stability of 1-3 under catalytic regime has been confirmed by FT-IR, UV/Vis, and resonance Raman spectroscopy. The reaction scope has been extended to alcohols, leading to the corresponding carbonyl compounds with yields up to 99 % under microwave (MW) irradiation. DFT calculations revealed that polyanions 1-3 have high-energy peroxo HOMOs, and a remarkable electron density localized on the peroxo sites as indicated by the calculated map of the electrostatic potential (MEP). This evidence suggests that the overall description of the oxygen-transfer mechanism should include possible protonation equilibria in water, favored for peroxo-POMs 1-3. Copyright
- Carraro, Mauro,Nsouli, Nadeen,Oelrich, Holger,Sartorel, Andrea,Soraru, Antonio,Mal, Sib Sankar,Scorrano, Gianfranco,Walder, Lorenz,Kortz, Ulrich,Bonchio, Marcella
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- Peroxo-Cerium(IV)-Containing Polyoxometalates: [CeIV6(O2)9(GeW10O37)3]24-, a Recyclable Homogeneous Oxidation Catalyst
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The class of peroxo-cerium-containing polyoxometalates has been discovered via the synthesis of the 9-peroxo-6-cerium(IV)-containing 30-tungsto-3-germanate, [CeIV6(O2)9(GeW10O37)3]24- (1). Polyanion 1 consists of a cyclic [Ce6(O2)9]6+ assembly that is stabilized by three dilacunary [GeW10O37]10- Keggin fragments. The title polyanion 1 is solution-stable, on the basis of 183W nuclear magnetic resonance, and was shown to act as a recyclable homogeneous catalyst for the selective, microwave-activated sulfoxidation of the model substrate methionine to the sulfoxide in the absence and to the sulfone in the presence of hydrogen peroxide. Solution and solid-state Raman as well as solid-state infrared studies of 1 demonstrated the complete loss (and regain) of the nine peroxo groups in situ during the catalytic cycle, suggesting that the peroxo-free {Ce6(GeW10)3} skeleton remains most likely intact during the catalytic cycle. Solid-state X-ray photoelectron spectroscopy measurements showed that peroxo loss is accompanied by reduction of the cerium ions from +4 to +3, which is fully reversible. Density functional theory calculations are in complete agreement with all of these observations and furthermore suggest that the reduction of the six cerium(IV) ions is accompanied by the formation of molecular dioxygen.
- Qasim, Hafiz M.,Ayass, Wassim W.,Donfack, Patrice,Mougharbel, Ali S.,Bhattacharya, Saurav,Nisar, Talha,Balster, Torsten,Solé-Daura, Albert,R?mer, Isabella,Goura, Joydeb,Materny, Arnulf,Wagner, Veit,Poblet, Josep M.,Bassil, Bassem S.,Kortz, Ulrich
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- A Donor-Acceptor [2]Catenane for Visible Light Photocatalysis
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Colored charge-transfer complexes can be formed by the association between electron-rich donor and electron-deficient acceptor molecules, bringing about the narrowing of HOMO-LUMO energy gaps so that they become capable of harnessing visible light. In an effort to facilitate the use of these widespread, but nonetheless weak, interactions for visible light photocatalysis, it is important to render the interactions strong and robust. Herein, we employ a well-known donor-acceptor [2]catenane - formed by the mechanical interlocking of cyclobis(paraquat-p-phenylene) and 1,5-dinaphtho[38]crown-10 - in which the charge-transfer interactions between two 4,4′-bipyridinium and two 1,5-dioxynaphthalene units are enhanced by mechanical bonding, leading to increased absorption of visible light, even at low concentrations in solution. As a result, since this [2]catenane can generate persistent bipyridinium radical cations under continuous visible-light irradiation without the need for additional photosensitizers, it can display good catalytic activity in both photo-reductions and -oxidations, as demonstrated by hydrogen production - in the presence of platinum nanoparticles - and aerobic oxidation of organic sulfides, such as l-methionine, respectively. This research, which highlights the usefulness of nanoconfinement present in mechanically interlocked molecules for the reinforcement of weak interactions, can not only expand the potential of charge-transfer interactions in solar energy conversion and synthetic photocatalysis but also open up new possibilities for the development of active artificial molecular shuttles, switches, and machines.
- ?or?evi?, Luka,Cai, Kang,Chen, Hongliang,Chen, Xiao-Yang,Feng, Yuanning,Jaynes, Tyler,Jiao, Yang,Mao, Haochuan,Qiu, Yunyan,Stoddart, J. Fraser,Stupp, Samuel I.,Wasielewski, Michael R.,Young, Ryan M.,Zhang, Long
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- Mo(VI) complex catalysed synthesis of sulfonees and their modification for anti-HIV activities
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An efficient method for the synthesis of sulfones has been developed using sugar derived cis-dioxo molybdenum(VI) complex as catalyst and urea hydrogen peroxide as oxygen source. Present method is highly specific for sulfide oxidation irrespective of presence of alkene and aldehyde groups in the same molecule. Synthesis of fifteen sulfones have been reported with 82–98% isolated yields and the catalyst has been reused five times without any loss in its activity. 2-(Phenylsulfonyl)aniline has been condensed with eight different aromatic aldehydes and the products are being explored for HIV-1 reverse transcriptase inhibition activities.
- Madduluri, Vimal Kumar,Baig, Noorullah,Chander, Subhash,Murugesan, Sankaranarayanan,Sah, Ajay K.
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- Kinetics and mechanism of iridium(III) catalysed oxidation of DL-methionine by alkaline hexacyanoferrate(III)
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Iridium(III) catalysed oxidation of DL-methionine by hexacyanoferrate(III) was studied spectrophotometrically in aqueous alkaline medium at 30 ± 0.1°C at a constant ionic strength. A micro amount of iridium(III) was sufficient to catalyse the slow reaction between DL-methionine and hexacyanoferrate(III). The reaction is first order in both hexacyanoferrate(III) and iridium(III) concentrations. The order with respect to DL-methionine is fractional. Increase in the alkali concentration increases the reaction rate. Methionine sulfone was found to be the main product of oxidation and it was identified by IR and mass spectra. Hexacyanoferrate(II), the other product was found to have no effect on reaction rate. The active species of oxidant and catalyst are [Fe(CN)6]3- and [IrCl3(H 2O)2OH]- respectively. A possible mechanism was proposed and the activation parameters were computed with respect to the slow step of the reaction.
- Dharma Rao,Baby Nirmala,Vani
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p. 365 - 371
(2013/05/22)
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- Halogenated fatty acid amides and cyclic depsipeptides from an eastern Caribbean collection of the cyanobacterium Lyngbya majuscula
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A lipophilic extract of an eastern Caribbean collection of Lyngbya majuscula yielded two new halogenated fatty acid amides, grenadamides B (1) and C (2), and two new depsipeptides, itralamides A (3) and B (4), along with the known compounds hectochlorin a
- Jimenez, Jorge I.,Vansach, Tifanie,Yoshida, Wesley Y.,Sakamoto, Bryan,Poerzgen, Peter,Horgen, F. David
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supporting information; experimental part
p. 1573 - 1578
(2010/03/31)
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- Under-flame Reaction of Sulfur-containing Amino Acids by a Hydrogen-Oxygen Flame
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Methionine was subjected to a flame-induced reaction in water or in an aqueous formic acid solution by using a hydrogen (50%)-oxygen (50%), hydrogen (87%)-oxygen (13%) and hydrogen diffusion flame. Besides the already-known stepwise oxidation by a hydroxyl radical, the contribution of a hydrogen atom from the flame to the reaction was recognized when the hydrogen-rich mixtures were employed. Homoserine was obtained under all the reaction conditions employed here, and glutamic acid when employing aqueous formic acid as a solvent. A common intermediate, the 3-carboxy-3-aminopropyl radical, appeared to exist in the reaction pathway. A coupling reaction of this radical with a hydrogen atom, hydroxyl radical and hydroxycarbonyl radical afforded 2-aminobutyric acid, homoserine and glutamic acid, respectively. Lanthionine and S-methylcysteine underwent the same reactions. Increasing the hydrogen content of the fuel and adding formic acid to the solvent resulted in retarding the reaction rate. The latter modification of the reaction system also brought about greater stability of the reaction products.
- Nomoto, Shinya,Shimoyama, Akira,Shiraishi, Susumu,Seno, Tomoyuki,Sahara, Denzo
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p. 643 - 649
(2007/10/03)
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- Flame-induced reactions of sulfur-containing amino acids in an aqueous solution
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Hydrogen-oxygen flames, when blown against an aqueous solution of methionine, induced conversion reactions to homoserine, 2-aminobutyric acid and glutamic acid. Besides the already-known reactions by a hydroxyl radical, a contribution of a hydrogen atom from hydrogen-rich flames to the reaction was recognized. We successfully controlled the vigorous oxidation of the system using a radical scavenger.
- Nomoto, Shinya,Shimoyama, Akira,Shiraishi, Susumu
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p. 1009 - 1012
(2007/10/03)
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- L-Methionine related 1-amino acids by acylase cleavage of their corresponding N-acetyl-DL-derivatives
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Acylase I from Aspergillus oryzae is an even more useful enzyme than suggested so far. Besides standard amino acids such as L-Met, L-Val and L-Phe, a number of additional sulfur- and selenium-containing amino acids can be obtained at useful reaction rates and in very high enantiomeric purity by kinetic resolution of the respective N-acetyl-DL-amino acids.
- Bommarius, Andreas S.,Drauz, Karlheinz,Guenther, Kurt,Knaup, Guenter,Schwarm, Michael
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p. 3197 - 3200
(2007/10/03)
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- Sulfonic peracids - III. Heteroatom oxidation and chemoselectivity
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We have investigated the p-toluenesulfonic peracid (2) generated in situ in the oxidation of different types of compounds containing nitrogen and/or sulfur. The sulfonic peracid 2 shows a remarkable chemoselectivity characterized by a preferred oxidation of sulfides to the sulfones in the presence of amines or olefins and a strong dependence on the nature of the amine in the competitive oxidation of olefins and amines.
- Kluge,Schulz,Liebsch
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p. 5773 - 5782
(2007/10/03)
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- Homogeneous Aqueous Oxidation of Organic Molecules by OxoneR and Catalysis by a Water-Soluble Manganese Porphyrin Complex
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Peroxymonosulfate (KHSO5) oxidizes a wide variety of water-soluble organic molecules in aqueous solutions, and the reactions are generally more rapid in phosphate buffer (pH 6-7) than in pure water.A water-soluble porphyrin complex, meso-tetrakis(4-N-methylpyridyl)porphyrinatomanganese(III) chloride, catalyzes epoxidation and hydroxylation under neutral pH conditions.
- Zheng, Tu-Cai,Richardson, David E.
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p. 833 - 836
(2007/10/02)
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- Optical Resolution and Asymmetric Transformation of (RS)-N-Alkyl- and (RS)-N,N-Dialkyl-2-phenylglycines
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Optical resolution of (RS)-N-methyl-2-phenylglycine and (RS)-N-ethyl-2-phenylglycine was carried out by using (1S)-10-camphorsulfonic acid as resolving agents, and that of (RS)-N-ethyl-N-methyl-2-phenylglycine by (R)- and (S)-1-phenylethylamine.Racemization rates of optically active Mpg, Epg, Emp, N,N-dimethyl-2-phenylglycine , and six α-amino acids were measured by heating in carboxylic acids.The electron-donating amino acid side chain and N-substituted alkyl group decreased therate to inhibit the formation of intermediary carbanions, whereas the electron-withdrawing side chain increased it.Asymmetric transformation of (RS)-Mpg, (RS)-Epg, and (RS)-Dmp was carried out on the basis of the results of optical resolution and racemization to give the corresponding enantiomers of approximately 100percent optical purities in over 70percent yield based on the sterting racemates.
- Shiraiwa, Tadashi,Baba, Yoshihisa,Miyazaki, Hideya,Sakata, Shinji,Kawamura, Seiko,et al.
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p. 1430 - 1437
(2007/10/02)
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- Oxidation of Thymines with Hydrogen Peroxide in Hydrochloric Acid
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Oxidation of thymine and 1,3-dimethylthymine with hydrogen peroxide in hydrochloric acid (pH 1.0-2.2) at 35-38 deg C gave the corresponding trans-5-chloro-6-hydroperoxy-5,6-dihydrothymines.The formation of the hydroperoxythymines was dependent on pH of the aqueous solutions.Reaction of the hydroperoxythymine with amino acids and nucleic acids related compounds in deuterium oxide was investigated by NMR spectroscopy.
- Itahara, Toshio
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p. 841 - 844
(2007/10/02)
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- Oxidation of Methionine by Sodium N-Bromobenzenesulphonamide in Aqueous Solution. A Kinetic and Mechanistic Study
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Kinetics of oxidation of DL-methionine (Mt) in the presence of HCl, HClO4, H2SO4 and NaOH by sodium N-bromobenzenesulphonamide (BAB) have been investigated at 40 deg (and 30 deg in alkaline medium).The rate law is identical in the three acids, .In alkaline medium, the rate law shows a first order dependence each on and ->.Effect of halide (Cl- or Br-) ion was studied.Addition of the reaction product, benzenesulphonamide retards the rate.Variation of ionic strength has no effect on the rate.The solvent isotope effect was studied using D2O.Activation parameters have also been determined.Methioninesulphone is identified as the reaction product.Mechanism proposed and the derived rate laws are in agreement with the observed kinetics.
- Ananda, S.,Rangappa, K. S.,Mahadevappa, D. S.
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p. 581 - 585
(2007/10/02)
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- Oxidation of Methionine by Sodium N-Chlorotoluene-p-sulphonamide in Aqueous Solution: a Kinetic Study
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Kinetics of oxidation of DL-methionine (Mt) in the presence of HCl, HClO4, H2SO4, and NaOH by sodium N-chlorotoluene-p-sulphonamide (CAT) have been investigated at 30 deg C (and 35 deg C in alkaline medium) and the results are compared with those obtained with HOCl as the oxidant, in acid medium.The reactions follow identical kinetics, being first order each in and +> and zero order in .In alkaline medium the rate shows first-order dependence each on and .An inverse fractional order is noted in ->.Studies of solvent isotope effects using D2O showed a retardation of rate both in acid and alkaline media.The derived rate laws are consistent with the observed kinetics.
- Mahadevappa, D.S.,Ananda, S.,Gowda, N.M. Made,Rangappa, Kanchugarakoppal S.
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- Kinetics and Mechanism of Oxidation of Methionine by Sodium N-Bromotoluenesulphonamide in Aqueous Solution
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Kinetics of oxidation of DL-methionine (Mt) in the presence of HClO4, HCl, H2SO4 and NaOH by bromamine-T (BAT) has been investigated at 45 deg C.Some rate law is obtained in all the acid media which depends on 1, 2 and 00.Halide ions catalyse the reaction.In alkaline medium, the rate law shows first order dependence each on 0 and and is independent of 0.Addition of the reaction product, p-toluenesulphonamide retards the reaction in the alkaline medium.Solvent isotope effect has been studied.Mechanisms proposed and the derived rate laws are in agreement with the observed results.
- Mahadevappa, D. S.,Mohan, K.
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p. 748 - 751
(2007/10/02)
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- A BIOMIMETIC HETEROATOM OXIDATION
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The oxidation of amines and sulfides to N-oxides, sulfoxides and sulfones is smoothly accomplished using 2-hydroperoxyhaxafluoro-2-propanol (HPHI).
- Ganem, Bruce,Biloski, Alan J.,Heggs, Richard P.
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p. 689 - 690
(2007/10/02)
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