- Synthesis and application of 2,3-Dihydroxybutanedioic Acid Esters as efficient additives in Methanol-Gasoline
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In this paper, 2,3-dihydroxybutanedioic acid esters (tartaric esters) were synthesized and used as phase stabilizer and saturation vapour pressure depressor of methanol-gasoline. The results show that the stabilities of the methanol-gasoline depend on the
- Jiang, Xiaoyan,Tang, Ying
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- Novel, low-cost, highly soluble n-type semiconductors: Tetraazaanthracene tetraesters
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New tetraester derivatives of 1,4,5,8-tetraazaanthracene have been prepared and characterized by spectroscopic and electrochemical techniques. The LUMO level of the compounds is close to -4 eV (the so-called air operating stability border in n-channel field effect transistors). Tetraesters were obtained with reasonable yields without the necessity of using high-quality reactants or solvents, resulting in their low cost.
- Gawrys,Marszalek,Bartnik,Kucinska,Ulanski,Zagorska
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- Superoxide dismutase mimetics. Part 2: Synthesis and structure-activity relationship of glyoxylate- and glyoxamide-derived metalloporphyrins
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Novel glyoxylate- and glyoxamide-derived metalloporphyrins 26-58 were synthesized and evaluated as potential superoxide dismutase (SOD) mimetics. Relative to previously studied MnTBAP analogues, the glyoxylate-derived metalloporphyrins 32, 39, and 54 and glyoxamide-derived metalloporphyrin 49, exhibited enhanced activity in the SOD assay and the majority of the analogues in the current series showed enhanced inhibition of lipid peroxidation and catalase activity.
- Trova, Michael P.,Gauuan, Polivina Jolicia F.,Pechulis, Anthony D.,Bubb, Stephen M.,Bocckino, Stephen B.,Crapo, James D.,Day, Brian J.
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- Synthesis of (E)-1-bromo-3-ethyl-3-pentene
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The synthesis of (E)-1-bromo-3-ethyl-3-pentene 1 is described in which the (E)-stereochemistry of the alkene is set up via a diastereoselective glyoxylate ene reaction.
- Brimble, Margaret A.,Edmonds, Michael K.
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- Enantioselective distribution of amino-alcohols in a liquid-liquid two-phase system containing dialkyl L-tartrate and boric acid
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Racemic amino-alcohols such as pindolol, propranolol, alprenolol and bucumolol enantiomers exhibited different distribution behaviors in a two-phase system consisting of a chloroform solution of didodecyl L-tartrate and an aqueous solution of boric acid. It seemed that a borate complex of the 1,2-diol group of the tartrate and the amino-alcohol was formed in the system. In the case of pindolol, one enantiomer was preferentially extracted into the organic phase (x 2.20) at equilibrium.
- Abe,Shoji,Kobayashi,Qing,Asai,Nishizawa
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- Retention Characteristics and Sorption Enthalpies of Esters of Natural Hydroxycarboxylic Acids on DB-1 Stationary Phase
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Abstract: Sorption characteristics and retention of esters of glycolic, lactic, malic, and tartaric acids with C1?C8 alcohols of linear structure are studied by gas-liquid chromatography in the temperature range of 90?260°C on DB-1 nonpolar phase. The values of the retention indices of the compounds studied are obtained. On the basis of experimentally determined retention times, the thermodynamic characteristics of sorption under the conditions of limiting dilution are estimated. The dependences of the change in sorption enthalpies on the length of the linear alkyl substituent and on the value of the logarithmic retention index are found. The possibility of estimating the energy of intermolecular interactions of lactic acid esters in the liquid phase is shown on the basis of the obtained values of sorption enthalpies and vaporization enthalpies.
- Portnova,Yamshchikova, Yu. F.,Krasnykh
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p. 577 - 583
(2019/06/03)
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- Synthetic Access to All Four Stereoisomers of Oxetin
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A short synthesis of all four stereoisomers of 3-amino-2-oxetanecarboxylic acid (oxetin) is described. The oxetane core is built using a Paternò-Büchi photochemical [2 + 2] cycloaddition; from the key intermediates, complementary resolution protocols provide access to enantiomerically pure oxetin and epi-oxetin on gram-scale.
- Kassir, Ahmad F.,Ragab, Sherif S.,Nguyen, Thao A. M.,Charnay-Pouget, Florence,Guillot, Régis,Scherrmann, Marie-Christine,Boddaert, Thomas,Aitken, David J.
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p. 9983 - 9991
(2016/11/02)
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- Zn(OTf)2-promoted chemoselective esterification of hydroxyl group bearing carboxylic acids
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Selective esterification of aliphatic and aromatic carboxylic acids with various alcohols is studied using triphenylphosphine, I2, and a catalytic amount of Zn(OTf)2. Use of this catalyst allows the formation of esters at a faster rate with good to excellent yield by activating the in situ generated acyloxyphosphonium ion intermediate. During the esterification process, both their aromatic and aliphatic hydroxyl groups are fully preserved from transesterification. The results show that the bulkiness and the reactivity of this doubly activated intermediate III control the selectivity and the rate of the reaction, respectively. The method is also useful for direct amidation reactions.
- Mamidi, Narsimha,Manna, Debasis
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p. 2386 - 2396
(2013/05/21)
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- Reductive coupling of aldehydes by H2S in aqueous solutions, a C-C bond forming reaction of prebiotic interest
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We report here a novel reductive coupling reaction of conjugated, non- or poorly enolizable aldehydes induced by H2S and operative in aqueous solutions under prebiotically relevant conditions. This reaction leads from retinal to β-carotene, and from benzylic aldehydes to the corresponding diarylethylenes. This novel reaction also opens a new potentially prebiotic pathway leading from glyoxylic acid to various compounds that are involved in the reductive tricarboxylic acid cycle. This C-C bond forming reaction of prebiotic interest might have been operative, notably, in the sulfide-rich environments of hydrothermal vents, which have been postulated as possible sites for the first steps of organic chemical evolution.
- Kajjout, Mohammed,Hebting, Yanek,Albrecht, Pierre,Adam, Pierre
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experimental part
p. 714 - 726
(2012/07/14)
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- Ionic liquids as solvent for efficient esterification of carboxylic acids with alkyl halides
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The selective esterification of carboxylic acid derivatives with a variety of alkyl halides was carried out using ionic liquid as solvent in the presence of triethylamine. The reaction was found to proceed under relatively mild conditions with excellent conversions (up to 99%) and selectivities. The ionic liquid was recycled and reused. TUeBITAK.
- Goek, Yetkin,Alici, Buelent,Cetinkaya, Enginc,OeZdemir, Ismail,Oezeroglu, Ozlem
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experimental part
p. 187 - 191
(2010/09/11)
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- Substituted porphyrins
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The present invention relates, in general, to a method of modulating physiological and pathological processes and, in particular, to a method of modulating cellular levels of oxidants and thereby processes in which such oxidants are a participant. The invention also relates to compounds and compositions suitable for use in such methods. Compounds of the invention include those of Formula I.
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- A CONVENIENT METHOD FOR ENZYMATIC BENZYL-ALKYL TRANSESTERIFICATION UNDER MILD NEUTRAL CONDITIONS
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Lipases from Candida cylindracea and from Pseudomonas fluorescens efficiently catalyse the benzyl to alkyl transesterification in organic solvents under mild conditions in nearly quantitative yields.
- Gutman, Arie L.,Shkolnik, Eleonora,Shapira, Michal
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p. 8775 - 8780
(2007/10/02)
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- Total Synthesis of the Antibiotic Sparsomycin, a Modified Uracil Amino Acid Monoxodithioacetal
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The total syntheses of sparsomycin (1), a naturally occurring antibiotic and antitumor substance, and its three stereomers 65-67 are described for the first time.In a convergent approach, the carboxylic acid 2 and the amine 3 were synthesized followed by amide formation (Scheme I).The acid 2 was prepared (23percent yield) from 6-methyluracil (12) by coupling the aldehyde 19 with the phosphorane 20 (Scheme III).The synthesis of the amine 3, especially challenging because of the monoxodithioacetal moiety, was accomplished by the reaction of a cysteine α-halo sulfoxide derivative 8 with sodium methylmercaptide (Scheme II, route B).Alternatively, oxidation of the dithioacetals 23-26 was unsatisfactory, yielding predominantly the undesired regioisomers 27B-30B (Table I).Procedures are given for the preparation and separation of the α-halo sulfoxide diastereomers 33,35, 36-41, and 52-54.By use of these procedures, the amino alcohol monoxodithioacetals 3 and 60 were prepared in five steps (40percent yield) from the D-cystine derivative 59 having the SC chirality of sparsomycin (Scheme VII).Finally, sparsomycin (1) and the SC diastereomer 67 were prepared (40percent yield) by mixed anhydride coupling of 2 with 3 and 60, respectively (Schemes I and X).In addition, syntheses of the RC enantiomer 65 and corresponding diastereomer 66 are described (Scheme IX).The CD spectra of 1 and its three stereomers are also discussed.
- Ottenheijm, Harry C.J.,Liskamp, Rob M.J.,Nispen, Simon P.J.M. van,Boots, Hans A.,Tijhuis, Marian W.
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p. 3273 - 3283
(2007/10/02)
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