- Oxidation of threonine by the analytical reagent diperiodatocuprate(III) - An autocatalysed reaction
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The kinetics of Cu(II) autocatalysed oxidation of threonine by well-recognized analytical reagent diperiodatocuprate(III) in aqueous alkaline medium at a constant ionic strength of 0.5 mol dm-3 was studied spectrophotometrically. The reaction between diperiodatocuprate(III) and threonine in alkaline medium exhibits 2:1 stoichiometry (DPC: threonine). The reaction is of first order in each [DPC] and [threonine] and less than unit order in [alkali]. Periodate has retarding effect on the rate of reaction. Ionic strength has negligible effect on the reaction. Increase in dielectric constant of the medium with decrease in the rate of the reaction was observed. The product, Cu(II), catalyses the reaction with a fractional order. The main products were identified by spot test and I.R. A composite mechanism involving the monoperiodatocuptrate(III) (MPC) as the reactive species of the oxidant in uncatalysed and autocatalysed reaction has been proposed. Activation parameters and the reaction constants involved in the different steps of the mechanisms are calculated.
- Jose, Timy P.,Tuwar, Suresh M.
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Read Online
- In-situ IR Spectroscopy Study of Reactions of C3 Oxygenates on Heteroatom (Sn, Mo, and W) doped BEA Zeolites and the Effect of Co-adsorbed Water
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The reactions of acetone and hydroxyacetone over heteroatom doped BEA zeolites (Sn, Mo, and W) in the presence and absence of H2O vapor are investigated using infrared spectroscopy. Acetone is converted to mesityl oxide over Sn-BEA exclusively. At higher temperatures, larger oxygenates such as phorones, aromatics, and coke form. The presence of co-adsorbed water in Sn-BEA suppresses tautomerization. H2O vapor is also beneficial for minimizing coke formation at high temperatures. Hydroxyacetone is converted into 2-hydroxypropanal over Sn-BEA, exhibiting high affinity to Sn sites up to 400 °C. Sn-BEA catalyzes conversion of hydroxyacetone into the enol in the absence of H2O, but exposure to H2O induces the formation of 2-hydroxypropanal and subsequent conversion to acrolein. The Lewis acid descriptors are used to rationalize the reaction pathways. For the isomerization of hydroxyacetone into 2-hydroxypropanal, the hardness of acid sites influences the reaction and correlates with the overall Lewis acidity of the catalysts, respectively. However, the size of the exchanged metal significantly affects aldol condensation, where keto and enol forms of acetone adsorb to active sites simultaneously.
- Najmi, Sean,So, Jungseob,Stavitski, Eli,McDermott, William P.,Lyu, Yimeng,Burt, Sam P.,Hermans, Ive,Sholl, David S.,Sievers, Carsten
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p. 445 - 458
(2020/12/01)
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- Method for preparing monoisopropanolamine
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The invention discloses a method for preparing monoisopropanolamine. The method comprises the steps of (a) reacting 1,2-propylene glycol under the action of a dehydrogenation catalyst to obtain 2-hydroxy propionaldehyde; and (b) reacting the 2-hydroxy propionaldehyde obtained in the step (1) with liquid ammonia and hydrogen under the action of a hydrogenation catalyst to prepare monoisopropanolamine. The dehydrogenation catalyst is prepared from a modified gamma-Al2O3 carrier and active components of CuO, PdO, Bi2O3 and In2O3. The hydrogenation catalyst comprises a modified gamma-Al2O3 carrierand active components NiO, V2O5 and Y2O3. Different catalysts and two-step reaction processes are adopted, and the reaction processes of dehydrogenation, imidization and hydrogenation of 1,2-propanediol are controlled to inhibit the generation of by-products such as hydroxyacetone in the dehydrogenation process and by-products such as secondary amine in the amination process, thereby greatly enhancing the yield and selectivity of the monoisopropyl alcohol product.
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Paragraph 0065; 0074-0075; 0090; 0094-0095
(2021/01/04)
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- Continuous catalytic process for the selective dehydration of glycerol over Cu-based mixed oxide
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The selective dehydration of glycerol to hydroxyacetone (acetol) was studied with Cu-based mixed oxides derived from hydrotalcite as catalysts in a continuous flow fix-bed reactor. Catalysts were prepared by co-precipitation and characterized by ICP, N2 adsorption, XRD, NH3-TPD, CO2-TPD, TPR and TEM. Different parameters were investigated to develop the most appropriate material as well as to determine the function of every metallic species. The optimized Cu-Mg-AlOx offered ≈60% acetol selectivity at >90% glycerol conversion (≈80% liquid yield, up to TOS = 9 h). The catalyst could be regenerated by calcination, achieving full activity recovery after five re-cycles. “In-situ” FTIR and XPS measurements evidenced that the presence of Cu, specially the most active Cu1+ species, was essential to carry out the dehydration to acetol with high reaction rates, and to form the preferred intermediate (with C[dbnd]O group); although a minor contribution from Cu0 and Cu2+ species could not be discarded.
- Concepción, Patricia,Domine, Marcelo E.,Mazarío, Jaime,Ventura, María
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p. 160 - 175
(2020/04/08)
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- Characterization of methylated azopyridine as a potential electron transfer mediator for electroenzymatic systems
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N,N'-dimethyl-4,4'-azopyridinium methyl sulfate (MAZP) was characterized as an electron transfer mediator for oxidation reactions catalyzed by NAD+- and pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases. The bimolecular rate constant of NADH reactivity with MAZP was defined as (2.2?±?0.1)?×?105?M?1?s?1, whereas the bimolecular rate constant of reactivity of the reduced form of PQQ-dependent alcohol dehydrogenase with MAZP was determined to be (4.7?±?0.1)?×?104?M?1?s?1. The use of MAZP for the regeneration of the cofactors was investigated by applying the electrochemical oxidation of the mediator. The total turnover numbers of mediator MAZP and cofactor NADH for ethanol oxidation catalyzed by NAD+-dependent alcohol dehydrogenase depended on the concentration of the substrate and the duration of the electrolysis, and the yield of the reaction was limited by the enzyme inactivation and the electrochemical process. The PQQ-dependent alcohol dehydrogenase was more stable, and the turnover number of the enzyme reached a value of 2.3?×?103. In addition, oxidation of 1,2-propanediol catalyzed by the PQQ-dependent alcohol dehydrogenase proceeded enantioselectively to yield L-lactic acid.
- Tetianec, Lidija,Chaleckaja, Ana,Kulys, Juozas,Janciene, Regina,Marcinkeviciene, Liucija,Meskiene, Rita,Stankeviciute, Jonita,Meskys, Rolandas
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- METHOD FOR PRODUCING ALDEHYDE
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PROBLEM TO BE SOLVED: To provide a new method for producing aldehyde capable of evading reduction under low temperature conditions and having higher selectivity. SOLUTION: Provided is a method for producing aldehyde where activated ester is prepared from carboxylic acid such as saturated fatty acid, unsaturated fatty acid, hydroxy acid, aromatic carboxylic acid and amino acid and an activation ester agent such as halogenated carbonic acid aryl, a carbodiimide-based condensation agent, an imidazole-based condensation agent and a triazine-based condensation agent, and the activated ester is reduced, and being a method for producing aldehyde in which an environmental load is reduce, and having high yield and high selectivity. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0016; 0017-0018
(2017/05/27)
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- Syntheses and biological evaluation of 1,2,3-triazole and 1,3,4-oxadiazole derivatives of imatinib
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Three novel series of 1,2,3-triazole and 1,3,4-oxadiazole derivatives of imatinib were prepared and evaluated in vitro for their cytostatic effects against a human chronic myeloid leukemia (K562), acute myeloid leukemia (HL60), and human leukemia stem-like cell line (KG1a). The structure-activity relationship was analyzed by determining the inhibitory rate of each imatinib analog. Benzene and piperazine rings were necessary groups in these compounds for maintaining inhibitory activities against the K562 and HL60 cell lines. Introducing a trifluoromethyl group significantly enhanced the potency of the compounds against these two cell lines. Surprisingly, some compounds showed significant inhibitory activities against KG1a cells without inhibiting common leukemia cell lines (K562 and HL60). These findings suggest that these compounds are able to inhibit leukemia stem-like cells.
- Li, Yong-Tao,Wang, Jing-Han,Pan, Cheng-Wen,Meng, Fan-Fei,Chu, Xiao-Qian,Ding, Ya-Hui,Qu, Wen-Zheng,Li, Hui-Ying,Yang, Cheng,Zhang, Quan,Bai, Cui-Gai,Chen, Yue
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p. 1419 - 1427
(2016/02/19)
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- Novel urushiols with human immunodeficiency virus type 1 reverse transcriptase inhibitory activity from the leaves of Rhus verniciflua
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Two novel urushiols, 1 and 2, and two known urushiols, 3 and 4, were isolated from the leaves of Rhus verniciflua and were examined for their human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) inhibitory activity. The novel urushiols were found to be 1,2-dihydroxyphenyl-3-[7(E),9(Z),11(Z)-pentadecatrienyl]-14-ol (1) and 1,2-dihydroxyphenyl-3-[8(Z),10(E),12(E)-pentadecatrienyl]-14-ol (2) by spectroscopic analyses. The absolute configuration at C-14 in 1 and 2 was determined to be a racemic mixture of (R) and (S) isomers by ozonolysis. Compound 2 (IC50: 12.6 μM) showed the highest HIV-1 RT inhibitory activity among the four urushiols, being 2.5-fold more potent than the positive control, adriamycin (IC50: 31.9 μM). Although the known urushiols were isolated from the sap and leaves of R. verniciflua, 1 was exclusively present in the leaves, and higher amounts of 2 were found in the leaves than in the sap. Present findings indicate that the leaves of R. verniciflua represent a new biological resource from which novel and known urushiols may be prepared, and the possible use of novel urushiols as bioactive products.
- Kadokura, Kazunari,Suruga, Kohei,Tomita, Tsuyoshi,Hiruma, Wataru,Yamada, Motoyuki,Kobayashi, Akio,Takatsuki, Akira,Nishio, Toshiyuki,Oku, Tadatake,Sekino, Yoshihiro
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p. 148 - 153
(2015/02/19)
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- Kinetics and mechanism of the oxidation of diols by butyltriphenylphosphonium dichromate
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The oxidation of four vicinal, four non-vicinal diols and one of their monoethers by butyltriphenylphosphonium dichromate (BTPPD), in dimethylsulfoxide (DMSO), resulted in the formation of corresponding hydroxyaldehyde as a main product of the oxidation. The reactions are of first order with respect to BTPPD, however, second order dependence is obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2-2H 4]ethanediol exhibited primary kinetic isotope effect (k H/kD = 6.61 at 298 K). The temperature dependence of the kinetic isotope effect suggested the symmetrical transition state in the rate-determining step. The rate constants of oxidation of four vicinal diols show excellent correlation with Taft's ∑ σ* values with negative reaction constant, ρz.ast;. The rate of oxidation of ethanediol has been determined in nineteen different solvents. An analysis of the solvent effect indicates the importance of the cation-solvating power of the solvents. A suitable mechanism has been postulated involving the formation of chromate ester in a pre-equilibrium.
- Panday, Dinesh,Kothari, Seema
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experimental part
p. 918 - 925
(2011/09/19)
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- Oxidation of some vicinal and non-vicinal diols by morpholinium chlorochromate: A kinetic and mechanistic study
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The kinetics of oxidation of four vicinal, four non-vicinal diols and two of their monoethers by morpholinium chlorochromate (MCC) have been studied in dimethylsulphoxide (DMSO). The main product of oxidation is the corresponding hydroxycarbonyl compound. The reaction is first order in MCC and the diols. The reaction is catalysed by hydrogen ions. The hydrogen ion dependence is taking the form : kobs = a + b [H+]. The oxidation of [1,1,2,2-2H4]ethanediol exhibits a substantial primary kinetic isotope effect (kH/kD = 5.82 at 298 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.
- Barthora,Baghmar,Agarwal,Sharma, Vinita
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experimental part
p. 677 - 683
(2012/04/10)
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- Selective catalytic oxidation of glycerol to dihydroxyacetone
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High selectivity and high yield characterize the oxidation of glycerol into dihydroxyacetone using catalyst 1, with benzoquinone or air as the oxidant. The mechanism proposed involves reversible palladium-alkoxide formation with the turnover-limiting reoxidation of the palladium complex. Copyright
- Painter, Ron M.,Pearson, David M.,Waymouth, Robert M.
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supporting information; experimental part
p. 9456 - 9459
(2011/03/19)
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- Zeolite H-USY for the production of lactic acid and methyl lactate from C3-sugars
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Lactic acid is an interesting platform chemical with many promising applications. This includes the use as a building block for the production of biodegradable plastics and environmentally friendly solvents. A study of the liquid-phase conversion of the triose-sugars, glyceraldehyde and dihydroxyacetone directly to methyl lactate and lactic acid catalyzed by inexpensive commercially available zeolites is presented. One particular zeolite, H-USY (Si/Al = 6) is shown to be quite active with near quantitative yields for this isomerization. Deactivation of the H-USY-zeolite was studied by correlating the catalytic activity to data obtained by TPO, XRD, N2-sorption, and NH3-TPD on fresh and used catalysts. Coking and irreversible framework damage occurs when lactic acid is produced under aqueous conditions. In methanol, methyl lactate is produced and catalyst deactivation is suppressed. Additionally, reaction rates for the formation of methyl lactate in methanol are almost an order of magnitude higher as compared to the rate of lactic acid formation in water.
- West, Ryan M.,Holm, Martin Spangsberg,Saravanamurugan, Shunmugavel,Xiong, Jianmin,Beversdorf, Zachary,Taarning, Esben,Christensen, Claus Hviid
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body text
p. 122 - 130
(2010/09/17)
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- Oxidative kinetics of serine and threonine by N-bromonicotinamide
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The kinetics of oxidative decarboxylation and deamination of α-amino acids, namely, serine and threonine by N-bromonicotinamide (NBN) in aqueous acetic acid medium (1:1) in presence of hydrochloric acid was studied over the temperature range 308-328 K. The oxidation reaction leads to the formation of corresponding aldehydes, CO2 and NH3. The reaction does not induce the polymerization of aerylonitrile. The reaction was found to be first order with respect to substrate concentration. Inverse first order was observed with respect to concentration of oxidant and mineral acid. Added nicotinamide retarded the reaction. Mercuric acetate had no significant effect on the reaction rate. A decrease in the dielectric constant of the medium increases the rate. HOBr has been postulated as the reactive oxidizing species in the reaction. The activation parameters were evaluated.
- Pushpalatha,Vivekanandan
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experimental part
p. 1027 - 1031
(2009/12/24)
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- METHOD OF PRODUCING LOWER ALCOHOLS FROM GLYCEROL
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A reactive-separation process converts glycerin into lower alcohols, having boiling points less than 2000C, at high yields. Conversion of natural glycerin to propylene glycol through an acetol intermediate is achieved at temperatures from 150° to 2500C at pressures from 1 and 25 bar. The preferred applications of the propylene glycol are as an antifreeze, deicing compound, or anti-icing compound. The preferred catalyst for this process in a copper-chromium.
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Page/Page column 58-59
(2008/06/13)
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- Characterizing NAD-dependent alcohol dehydrogenase enzymes of Methylobacterium extorquens and strawberry (Fragaria x ananassa cv. Elsanta)
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The methylotroph Methylobacterium extorquens (strain with CABI registration number IMI 369321), which has been isolated from strawberry (Fragaria x ananassa cv. Elsanta) callus cultures, was grown on a mixture of methanol (0.25% v/v) and 1,2-propanediol (0.75% v/v). The microbial biotransformation of 1,2-propanediol to 2-hydroxypropanal (lactaldehyde) was studied. The bacterial alcohol dehydrogenase (ADH) enzymatic activities were assessed, and the optimum pH for ADH activity was found to be pH 6.0. Enzyme assays were carried out for both the bacterial and the strawberry extracts to define the best substrate specificity. For Methylobacterium extorquens, the best substrates were found to be methanol (Km = 0.78 mM) and 1,2-propanediol (Km = 15.84 mM), whereas for strawberries, 1-propanol (Km = 3.54 mM) and ethanol (Km = 6.66 mM) were the best substrates. A wide variety of metals as well as EDTA were shown to decrease the enzymatic activity. Furthermore, SDS-PAGE experiments showed molecular weights of 45.0 and 24.6 kDa for the alcohol dehydrogenases of Methylobacterium extorquens and Fragaria x ananassa, respectively.
- Koutsompogeras, Panagiotis,Kyriacou, Adamantini,Zabetakis, Ioannis
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p. 235 - 242
(2007/10/03)
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- Borate as a phosphate ester mimic in aldolase-catalyzed reactions: Practical synthesis of L-fructose and L-iminocyclitols
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Dihydroxyacetone phosphate (DHAP)-dependent aldolases have been widely used for the organic synthesis of unnatural sugars or derivatives. The practicality of using DHAP-dependent aldolases is limited by their strict substrate specificity and the high cost and instability of DHAP. Here we report that the DHAP-dependent aldolase L-rhamnulose 1-phosphate aldolase (RhaD) accepts dihydroxyacetone (DHA) as a donor substrate in the presence of borate buffer, presumably by reversible in situ formation of DHA borate ester. The reaction appears to be irreversible, with the products thermodynamically trapped as borate complexes. We have applied this discovery to develop a practical one-step synthesis of the non-caloric sweetener L-fructose. L-Fructose was synthesized from racemic glyceraldehyde and DHA in the presence of RhaD and borate in 92% yield on a gram scale. We also synthesized a series of L-iminocyclitols, which are potential glycosidase inhibitors, in only two steps.
- Sugiyama, Masakazu,Hong, Zhangyong,Whalen, Lisa J.,Greenberg, William A.,Wong, Chi-Huey
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p. 2555 - 2559
(2007/10/03)
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- Process for preparing dioxy-functionalized propane compounds
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The present invention relates to a process for preparing, dioxy functionalised propane compounds using cobalt and/or rhodium catalysts. More particularly, the present invention relates to a process for the preparation of the dioxy functionalised propane compounds of the formula X—CH2—CH(Y)—CH2-Z, wherein X=R—C(=O)—O— or H or —OH, Y and Z=—H or —OH or —C(=O)H, and wherein at a time, only one of X, Y and Z is —H, in high yields from vinyl carboxylates of formula R—C(=O)—O—CH=CH2 wherein, R=substituted or unsubstituted alkyl or aryl group.
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Page/Page column 11
(2010/02/14)
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- Rate constants for the gas-phase reactions of OH radicals with a series of hydroxyaldehydes at 296 ± 2 K
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Using a relative rate method with in situ generation of the hydroxyaldehydes, rate constants for the reactions of the OH radical with 2-hydroxybutanal [CH3CH2CH(OH)CHO], 3-hydroxybutanal [CH3CH(OH)CH2CHO], 2-hydroxypropanal [CH 3CH(OH)CHO], 2-hydroxy-2-methylpropanal [(CH3) 2C(OH)CHO], and 3-hydroxy-propanal [HOCH2CH 2CHO] have been measured at atmospheric pressure and 296 ± 2 K. The hydroxy-aldehydes were generated in situ from the OH radical-initiated reactions of precursor compounds (1,2- and 1,3-butanediol, 2-methyl-2,4-pentanediol, 2-methyl-3-buten-2-ol, and cis-3-hexen-1-ol) and the rate constants for the reaction of OH radicals with the hydroxyaldehydes were determined relative to those for reaction of OH radicals with the precursor compound. The rate constants obtained (in units of 10-11 cm 3 molecule-1 s-1) were CH3CH 2CH(OH)CHO, 2.37 ± 0.23; CH3CH(OH)CH 2CHO, 2.95 ± 0.24; CH3CH(OH)CHO, 1.70 ± 0.20; (CH3)2C(OH)CHO, 1.40 ± 0.25; and HOCH 2CH2CHO, 1.99 ± 0.29.
- Baker, Jillian,Arey, Janet,Atkinson, Roger
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p. 7032 - 7037
(2007/10/03)
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- Kinetics of oxidative degradation of threonine by alkaline permanganate
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The kinetics of oxidation of threonine by permanganate in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between permanganate threonine in alkaline medium exhibits 1:2 stoichiometry (KMnO4: threonine). The reaction shows first order dependence of rate on permanganate concentration and less than unit order dependence each in threonine and alkali concentrations. Reaction rate increases with an increase in ionic strength and a decrease in solvent polarity of the medium. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the formation of an intermediate complex between oxidant and substrate has been proposed. The rate constants and the activation parameters for the slow step of the mechanism have been evaluated and discussed.
- Mavalangi, Surekha K.,Pol, Pandurang D.,Nandibewoor, Sharanappa T.
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p. 181 - 193
(2007/10/03)
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- Aldolase-catalyzed asymmetric synthesis of novel pyranose synthons as a new entry to heterocycles and epothilones
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Enzymatic reactions catalyzed by DERA provide the basis for a new strategy for the synthesis of novel pyranose synthons. The utility of this very convergent and effective method is demonstrated by the concise total synthesis of epothilones (see scheme; DERA = 2-deoxyribose-5-phosphate aldolase).
- Liu, Junjie,Wong, Chi-Huey
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p. 1404 - 1407
(2007/10/03)
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- Kinetics and mechanism of oxidation of amino acids by N-chloronicotinamide in aqueous acetic acid medium
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Kinetics of oxidation of ten α-amino acids by N-chloronicotinamide (NCN) in aqueous acetic acid medium in presence of hydrochloric acid have been investigated. The observed rate of oxidation is first order in both [oxidant] and [HCl]. A small increase in rate is observed with increase in [amino acid]. A decrease in the dielectric constant of the medium increases the rate. Addition of nicotinamide (NA), the reduction product of NCN, has a retarding effect on the rate of oxidation. The corresponding aldehydes, ammonia and carbon dioxide have been identified as the oxidation products. Molecular chlorine has been postulated as the reactive oxidising species in the reaction.
- Vivekanandan,Nambi
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p. 198 - 201
(2007/10/03)
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- Kinetics and mechanism of oxidation of diols by quinolinium fluorochromate
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The kinetics of oxidation of four vicinal diols, four non-vicinal diols and two of their monoethers by quinolinium fluorochromate (QFC) have been studied in dimethylsulphoxide. The main product of oxidation is the corresponding hydroxycarbonyl compound. The reaction is first order in QFC. Michaelis-Menten type kinetics have been observed with respect to the diols. The oxidation of [1,1,2,22H4] ethanediol exhibits a substantial primary kinetic isotope effect (k(H)/k(D) = 6.35 at 303 K). The reaction has been in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equation. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.
- Choudhary, Kirti,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 325 - 330
(2007/10/03)
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- Monitoring carbonyl-amine reaction and enolization of 1-hydroxy-2- propanone (acetol) by FTIR spectroscopy
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Infrared absorption bands characteristic of the aldehydo, keto, and enediol forms of 1-hydroxy-2-propanone (acetol) were identified and used to study the effect of solvent on the absorption frequencies and the effect of temperature and acid/base catalysis on the enolization reactions. The data indicated that, in addition to water, acids and bases can catalyze the enolization of 1-hydroxy-2-propanone and that the temperature inversely effects the rate of enolization under basic conditions. However, under acidic conditions, increasing the temperature favors the enolization process. In addition, the reaction of 1-hydroxy-2-propanone with a primary and a secondary amine was also monitored by Fourier transform infrared spectroscopy. The data indicated that at room temperature the rate of amine reaction was faster than the rate of its catalysis of enolization; however, below room temperature, the rate of base-catalyzed enolization became comparable with the rate of carbonyl-amine reaction forming both Heyns and Amadori adducts.
- Yaylayan, Varoujan A.,Harty-Majors, Susan,Ismail, Ashraf A.
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p. 2335 - 2340
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Diols by Pyridinium Bromochromate
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The kinetics of oxidation of four vicinal diols, four nonvicinal diols, and one of their monoethers by pyridinium bromochromate (PBC) have been studied in dimethyl sulfoxide.The main product of oxidation is the corresponding hydroxyaldehyde.The reaction is first-order with respect to each the diol and PBC.The reaction is acid-catalyzed and the acid dependence has the form: kobs = a + b+>.The oxidation of ethanediol exhibited a primary kinetic isotope effect (kH/kD = 6.70 at 298 K).The reaction has been studied in 19 organic solvents including dimethyl sulfoxide and the solvent effect has been analyzed using multiparametric equations.The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step.A suitable mechanism has been proposed.
- Rao, P. Surya Chandra,Suri, Deepa,Kothari, Seema,Banerji, Kalyan K.
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p. 285 - 290
(2007/10/03)
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- Synthesis of aldehydes from carboxylic acids via 2-imidazolines
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The use of readily available 2-substituted-2-imidazolines as precursors to 2-hydroxy aldehyde, unsaturated aldehyde and a variety of functionalized aldehydes is reported. It provides a novel method for the preparation of aldehydes from carboxylic acids via 2-substituted-2-imidazolines.
- Shi, Zhen,Gu, Huan
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p. 2701 - 2707
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Diols by 2.2'-Bipyridinium Chlorochromate
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The kinetics of oxidation of four vicinal diols. four non-vicinal diols and two of their monoethers by 2.2'-bipyridinium chlorochromate (BPCC) have been studied in dimethyl sulfoxide.The main product of oxidation is the corresponding hydroxycarbonyl compound.The reaction is first order with respect to both BPCC and the diol.The oxidation of ethanediol exhibits a substantial primary kinetic isotope effect (kN/kD = 6.35 at 303 K).The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equations.The temperature dependence of the kinetic isotope effect indicates the presence of a symetrical transition state in the rate-determining step.A suitable mechanism has been proposed.
- Loonker, Kavita,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 1663 - 1680
(2007/10/03)
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- Manganese (III) oxidation of some neutral amino acids in pyrophosphate medium: A kinetic and mechanistic study
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Kinetics of oxidation of L-serine, L-phenylalanine, DL-alanine, DL-valine and DL-threonine (AA) by manganese (III) ions have been studied as a function of pH (0.91-1.45) at 328K. The reaction shows a first order dependence each in [MnIII]o and [AA]o, inverse fractional order each in the added [Na4P2O7] and [Mn11] and a fractional order in [H+]. Effect of the added anions and varying solvent composition have also been studied. Solvent isotope studies have been made in D2O medium. Activation parameters are computed from Arrhenius-Eyring plots. An isokinetic relationship is noted and the isokinetic temperature β=340K, indicating enthalpy control on the reactions. Taft linear free energy relationship is observed with p = -0.43 indicating an electron deficiency transition state. A mechanism consistent with the observed results is proposed and discussed.
- Chandraju,Mahadevappa,Rangappa
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p. 974 - 980
(2007/10/03)
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- Role of α-substituent on the oxidation of a-amino acids by bromine in acid medium
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The kinetics of oxidation of amino acids by bromine in aqueous perchloric acid medium at 35°C has been studied. Based on the experimental results, a reaction scheme is proposed in which the active oxidants are bromine and HOBr. The electrophilic attack of bromine occurs at the carboxylate (-COO-) group. HOBr reacts with the amino acids through the a-hydrogen atom via hydride ion transfer or abstraction. The α-substituent plays a vital role in accelerating the rate limiting step.
- Ramachandran,Easwaramoorthy,Sayeekannan,Vasanthkumar
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p. 696 - 700
(2007/10/03)
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- N-(α-ALKOXYALKYL)AMINES VI. THE THERMODYNAMICS OF ISOMERIZATION AND THE KINETICS OF ACID HYDROLYSIS OF THE DIASTEREOMERS OF 9-(1-METHOXY-2-HYDROXYPROPYL)CARBAZOLE
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The kinetics of the acid hydrolysis and the thermodynamics of the isomerization of the threo and erythro diastereomers of 9-(1-methoxy-2-hydroxypropyl)carbazole were studied.It was shown that hydrolysis takes place by an A1 mechanism with the formation of β-hydroxycarbenium-immonium ion in the controlling stage.The threo and erythro diastereomers differ little in hydrolytic activity.In the ground state the threo diastereomer is thermodynamically more stable than the erythro diastereomer on account, probably, of the formation of an intramolecular hydrogen bond OH...OCH3 in the most highly populated conformation of the threo diastereomer.This was confirmed by calculations of the conformations of the threo and erythro isomers of 9-(1-methoxy-2-hydroxypropyl)carbazole by molecular mechanics.
- Anfinogenov, V.A.,Zuikova, S. A.,Khlebnikov, A. I.,Ogorodnikov, V. D.
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p. 447 - 451
(2007/10/02)
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- 6-Deoxy-L-lyxo- and 6-Deoxy-L-arabino-hexulose 1-phosphates. Enzymic Syntheses by Antagonistic Metabolic Pathways
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Efficient large-scale syntheses of the title compounds (up to 0.1 mole) from readily available precursors have been accomplished along destructive as well as constructive biosynthetic routes by employing overexpressed enzymes from E. coli.The first route, which consists of an aldose isomerization-ketose phosphorylation sequence, utilizes natural L-fucose and L-rhamose as the respective sources of chirality.The key reaction of the second route, which starts from racemic 2-hydroxypropanal and achiral dihydroxyacetone phosphate, is a diastereospecific aldol addition with complete kinetic resolution.
- Fessner, Wolf-Dieter,Schneider, Achim,Eyrisch, Oliver,Sinerius, Gudrun,Badia, Josefa
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p. 1183 - 1192
(2007/10/02)
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- Autocatalysis in the oxidation of α-aminoacids
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The oxidative decarboxylation of eleven α-amino acids (AA) by N-bromoacetamide (NBA) are studied.The integrated first order equation for the disappearance of NBA shows curvature towards time axis even at the early stages of the reaction while the plots versus time are linear even upto 75percent conversion of the oxidant.The rate equation obeys -d/dt = (ka + kb).The influence of -> on kobs is observed in glycine, alanine and to a smaller extent in serine and threonine.The kinetic scheme involves the formation of a complex intermediate between N-bromoacetamide and amino acid anion which then decomposes in the rate limiting step.The absorption spectrum of the reaction mixture shows the formation of imine as the intermediate which may catalyse the reaction.
- Ramachandran, M S,Easwaramoorthy, D,Raj, R P Malim Mani,Vivekanandam, T S
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p. 332 - 337
(2007/10/02)
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- Additive Pummerer reactions of vinylic sulfoxides. Synthesis of γ-hydroxy-α,β-unsaturated esters, α-hydroxyketones, and 2-phenylsulfenyl aldehydes and primary alcohols
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Treatment of β-monosubstituted vinylic sulfoxides 1 with trifluoroacetic anhydride in dichloromethane gave excellent yields of 1,2-bis(trifluoroacetoxy)thioethers 6. Mildly basic methanolysis of 2-alkyl-substituted 6 gave α-hydroxyaldehydes 11 as monomer-dimer mixtures; similar treatment of the 2-aryl analogues afforded aryl (hydroxymethyl) ketones 12. Compounds 11 underwent Wittig reactions with methoxycarbonylmethylenetriphenylphosphorane to give high yields of γ-hydroxy-α,β-unsaturated esters 13, predominantly as the E-isomers. β-Monosubstituted vinylic sulfoxides 1 possessing a β-aryl group, and β-disubstituted vinylic sulfoxides 3 reacted with trifluoromethanesulfonic anhydride-sodium acetate in acetic anhydride to give 2-(phenylsulfenyl) acylals 14. These gave 2-phenylsulfenyl aldehydes 15 upon basic methanolysis, and the corresponding primary alcohols 16 on reduction with sodium borohydride. Reaction of both geometric isomers of enantiomerically pure vinylic sulfoxide 1o with TFAA gave racemic 6o as a mixture of diastereomers. Reaction of optically pure (E)- and (Z)-1p with trifluoromethanesulfonic anhydride-sodium acetate in acetic anhydride gave acylal 19 in 10.5 and 23% e.e., respectively.
- Craig, Donald,Daniels, Kevin,MacKenzie, A. Roderick
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p. 11263 - 11304
(2007/10/02)
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- Kinetics and mechanism of oxidation of serine, threonine, arginine, aspartic acid and glutamic acid by N-bromoacetamide in alkaline medium
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The title amino acids are oxidised to the corresponding aldehydes, ammonia and carbon dioxide.The effect of varying , , -> and ionic strength have been studied.The data reveal that the reaction is first order in and fractional order each in and ->.Addition of acetamide does not affect the rate of oxidation.Thermodynamic parameters have been calculated and a suitable mechanism consistent with the experimental results is proposed.
- Reddy, M. Komal,Sribabu, Ch.,Sundaram, E. V.
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- Derivatives of 13-deoxycarminomycin
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An anthracycline compound (13-deoxycarminomycin) selected from the group consisting of anthracycline compounds represented by the following formula STR1 R1 is a hydroxy group, R2 represents a hydrogen atom or a hydroxyl group, R3 is a hydrogen atom, R4 represents one of the following groups (a) to (d) STR2 and if R2 is hydroxyl, R4 is not (d).
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- Effect of Formaldehyde on Kinetics and Mechanism of Oxidation of Amino Acids by Bromamine-T in Perchloric Acid Medium
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The kinetics of oxidation of amino acids by bromamine-T (BAT) have been investigated both in the presence and absence of formaldehyde in perchloric acid medium.The reaction is first order in , zero order in both and and fractional order in in the presence of formaldehyde, and first order each in , and and inverse first order in in the absence of formaldehyde.Addition of p-toluenesulphonamide or variation in ionic strength of the medium does not have any significant effect on the rate, but the decrease in dielecrtic constant of the reaction medium decreases the rate.Activation parameters have been computed from the Arrhenius plots and mechanisms in conformity with the observed kinetics have been suggested and related rate laws deduced.The oxidation process in the presence of formaldehyde proceeds via two pathways.
- Gowda, B. Thimme,Rao, R. Vijayalakshmi
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- Kinetics and Mechanism of Ruthenium(III)-Catalysed Oxidation of Amino Acids by Peroxodiphosphate in Acid Medium
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The kinetics of oxidation of amino acids (AA) such as glycine, alanine, phenylalanine, serine, threonine, aspartic acid and glutamic acid by peroxodiphosphate (PP) in presence of Ru(III) have been studied.The reactions are found to be acid-catalysed and an analysis of rate dependence on reveals that the active oxidizing species is H3P2O8(-).The Ru(III)-catalysis of PP-AA reaction is explained in terms of formation of a 1:1 complex between Ru(III) and AA, which later reacts with PP to give the products.The products obtained are ammonia, carbon dioxide and the corresponding aldehyde.
- Rao, M. Anand
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p. 417 - 419
(2007/10/02)
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- Effect of Chloride Ion on Kinetics of Oxidation of Threonine by Chloramine-T in Acid Medium
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Effect of chloride on the kinetics of oxidative decarboxylation and deamination of threonine (Thr) by chloramine-T (CAT) has been studied in HClO4 medium at 303 K.The reaction has been investigated over a wide range of (0.001-0.2 mol dm-3) both in the presence and absence of Cl(-).It has been observed that the catalytic effect of Cl(-) is dependent.The effect is more pronounced at > 0.03 mol dm-3.The change of either or has no effect on the kinetic order in .But the order in , , and change with the and .The effects of added reaction product, and variation of ionic strength and dielectric constant of the medium on the rate have been investigated.Activation parameters have also been computed.Rate laws in agreement with the experimental results have been deduced by proposing appropriate mechanistic schemes.
- Gowda, B. Thimme,Sherigara, B. S.
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p. 960 - 963
(2007/10/02)
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- Chemoselective Oxidation of the Primary Alcohol Function of Diols Catalyzed by Zirconocene Complexes
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Zirconocene complexes, Cp2ZrH2 and Cp2Zr2, catalyze the Oppenauer-type oxidation of alcohol functions to the corresponding carbonyl compounds in the presence of an appropriate hydrogen acceptor such as benzophenone.In the oxidation of primary α,ω-diols and of diols containing two secondary alcohol functions, one of the alcohol functions is selectively oxidized to form hydroxy aldehydes and hydroxy ketones, respectively, in substantial yields.The chemoselective oxidation of the primary alcohol function can be achieved in the oxidation of diols containing both the primary and secondary alcohol functions.
- Nakano, Tatsuya,Terada, Takanobu,Ishii, Yasutaka,Ogawa, Masaya
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p. 774 - 776
(2007/10/02)
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- Kinetics of Oxidation of Amino Acids by Sodium N-Bromo-p-toluenesulphonamide in Alkaline Medium
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Kinetics and mechanism of oxidation of several amino acids by sodium N-bromo-p-toluenesulphonamide (BAT) has been investigated in the alkaline medium.Generally the reaction is first order in and zero order in at both low and high .The rate is independent of at low and the reaction is fractional order in at high .The effects of added halide ion, p-toluenesulphonamide and varying ionic strength and dielectric constant of the medium on the rate have been studied.The activation parameters have been computed as a function of the dielectric constant of the medium.Rate laws consistent with the experimental results have been deduced and suitable mechanisms have been proposed.
- Gowda, B. Thimme,Rao, R. Vijayalakshmi
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p. 1021 - 1025
(2007/10/02)
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- Enzymatic vs. Fermentative Synthesis: Thermostable Glucose Dehydrogenase Catalyzed Regeneration of NAD(P)H for use in Enzymatic Synthesis
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Procedures are described for regeneration of reduced nicotinamide cofactors NADH and NADPH from NAD(P) based on glucose and a thermostable glucose dehydrogenase from Bacillus cereus immobilized in polyacrylamide gels.The turnover number for NAD in a synthesis of 200 mmol of D-lactate is 40000.Application of this system to other syntheses is demonstrated with preparations of ethyl (R)-4-chloro-3-hydroxybutanoate, (R)-2,2,2-trifluoro-1-phenylethanol, ethyl (S)-3-hydroxyvalerate, (S)-lactaldehyde dimethyl acetal, and (S)-3-hydroxybutanal dimethyl acetal.Further investigation of the kinetics regarding the thermoresistance of glucose dehydrogenase in the presence of NaCl has been carried out, and it appears that the enhancement by NaCl of the thermal stability of the enzyme is approximately third order.The immobilized glucose dehydrogenase incubated at 55 deg C, pH 7.5, for 7 days is still fully active while many other enzymes are completely inactivated in 1-2 days.Addition of NaCl enhances the thermal stability more significantly than the immobilization does, and a remarkable increase in thermal stability was observed with these two combined factors.The half-life of the immobilized glucose dehydrogenase at 55 deg C in a buffer (pH 7.0-7.5) containing 1 M NaCl is more than 30 days compared to 3 min for the free enzyme, corresponding to an overall ca. 50000-fold increase in thermal stability.
- Wong, Chi-Huey,Drueckhammer, Dale G.,Sweers, Henri M.
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p. 4028 - 4031
(2007/10/02)
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- Preparation of Manganic Sulphate in Sulphuric Acid and Kinetics of Its Reaction with Threonine
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Spectroscopic studies have been made on the equilibrium Mn(II) + Mn(IV)2Mn(III) in the presence of excess and .Results show that when is twice that of , Mn(IV) is quantitatively converted into Mn(III) and this principle can be used to prepare manganic sulphate.Oxidation of threonine by Mn(III) follows second order kinetics in , first order in , inverse first order in and inverse second order in .The reaction shows positive salt effect.Suitable machanism is proposed and discussed based on the kinetic results.
- Ramachandran, M. S.,Vivekanandam, T. S.,Kader, S. Syed
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p. 379 - 382
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Diols by Pyridinium Chlorochromate in Dimethyl Sulphoxide
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The kinetics of oxidation of several diols and two of their mono ethers by pyridinium chlorochromate (PCC) have been studied in DMSO.The principal product of the oxidation is the corresponding hydroxyaldehyde.The reaction is first order each in and .The oxidation of ethanediol-1,1,2,2-d4 exhibits a primary kinetic isotope effect, kH/kD = 6.75 at 298 K.The activation energies and entropies of the oxidation of the diols and their monoethers are linearly related.The reaction involves transfer of a hydride ion in the rate-determining step.The temperature dependence of the kinetic isotope effect points to a planar pericyclic transition state.
- Banerji, Kalyan, K.
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p. 650 - 652
(2007/10/02)
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- Kinetics and mechanism of osmium (VIII) and ruthenium (III) catalyzed oxidation of ethanediol and propane 1 : 2 diol with chloramine-T in alkaline and acid media
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The kinetics of oxidation of title diols by chloramine-T (CAT) is studied in HCl medium (0.01-0.80 M), catalyzed by Ru(III) chloride at 35 deg C and in NaOH medium (0.001-0.012 M) with OsO4 as catalyst at 50 deg C.Simultaneous catalysis is effected by H+ and Cl- in acid medium in the lower range (0.01-0.15 M), the rate law being -d log /DT = >/> which changes to k'1- at medium ranges and becomes independent of 1-> at higher acid concentration (>0.4 M).Alkali retards the Os(VIII) catalyzed reaction and the rate law takes the form -d log 1-.Ionic strength and added reaction product, p-toluene-sulphonamide (RNH2) had no significant effect on the reaction rate at lower and high acid concentrations and in alkaline medium, but in the acid range (0.20-0.40 M), increase in ionic stength decreases the rate of oxidation.Decrease in dielectric constant of the reaction medium decreases the rate constant in both media.The reaction was studied at different temperatures and Arrhenius parameters have been evaluated.Suitable mechanisms have been proposed to account for the observed kinetics.
- Naidu, H. M. K.,Katgeri, S. N.,Mahadevappa, D. S.
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p. 469 - 480
(2007/10/02)
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- EFFECT OF OXYGEN ON THE TRANSFORMATION OF THE RADICALS OF α-DIOLS
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The effect of oxygen on the oxidation and oxidative degradation of 1,2-propanediol, 2,3-butanediol, and ethyl glycol monomethyl ether was investigated.It was shown that the dehydration processes in the radicals of the α-diols are suppressed in the presence of oxygen, and these are accompanied by their oxidation and/or oxidative degradation.The mechanism of the processes is discussed on the basis of the obtained data.
- Petryaev, E. P.,Maslovskaya, L. A.,Shadyro, O. I.
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p. 1973 - 1976
(2007/10/02)
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- The Mechanism of Ozone-Alkene Reactions in the Gas Phase. A Mass Spectrometric Study of the Reactions of Eight Linear and Branched-Chain Alkenes
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The stable products of the low-pressure (4 - 8 torr (1 torr = 133.33 Pa)) gas-phase reactions of ozone with ethene, propene, 2-methylpropene, cis-2-butene, trans-2-butene, trans-2-pentene, 2,3-dimethyl-2-butene, and 2-ethyl-1-butene have been identified by using a photoionization mass spectrometer coupled to a stirred-flow reactor.The products observed are characteristic of (i) a primary Criegee split to an oxoalkane (aldehyde or ketone) and a Criegee intermediate, (ii) reactions of the Criegee intermediates such as unimolecular decomposition, secondary ozonide formation, etc., and (iii) secondary alkene chemistry involving OH and other free-radical products formed by the unimolecular decomposition of the Criegee intermediates.The secondary OH - alkene - O2 reactions account for a significant fraction of the alkene (CnH2n) consumed and lead to characteristic products such as Cn dioxoalkanes nH2n + 30)>, Cn acyloins nH2n + 32)>, and Cn alkanediols nH2n + 34)>.Cn oxoalkanes and Cn epoxyalkanes observed at m/e (CnH2n + 16) are probably formed primarily via epoxidation of the alkene by O3.A general mechanism has been proposed to account for the observations.
- Martinez, Richard I.,Herron, John T.,Huie, Robert E.
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p. 3807 - 3820
(2007/10/02)
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- 1-N-alkyl-aminoglycoside-XK-88 derivatives and methods for their manufacture
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1-N-Alkyl-Aminoglycoside-XK-88 derivatives, valuable as antibacterial agents, are prepared by the reaction of an acid addition salt of the corresponding 1-N-unsubstituted-Aminoglycoside-XK-88 antibacterial derivative or of a 2"-N-alkanoyl-Aminoglycoside-XK-88-5 derivative in an inert solvent, preferably a protic solvent containing water, with one equivalent of a hydride-donor reducing agent and with at least one equivalent of an aldehyde. The 2"-N-alkanoyl-Aminoglycoside-XK-88-5 intermediates are prepared by the reaction of a partially neutralized acid addition salt of Aminoglycoside-XK-88-5 with an acylating agent, and isolating the 2"-N-alkanoyl-Aminoglycoside-XK-88-5.
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- Di-N-alkylaminoglycosides, methods for their manufacture and novel intermediates useful therein, method for their use as antibacterial agents and pharmaceutical compositions useful therefor
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1,2'-di-N-4,6-di-O-(aminoglycosyl)-1,3-diaminocyclitols and 1,6'-di-N-alkyl-4,6-di-O-(aminoglycosyl)-1,3-diaminocyclitols and their acid addition salts are valuable as antibacterial agents. Also disclosed are 2'-N-alkyl-4,6-di-O-(aminoglycosyl)-1,3-diaminocyclitol antibacterial agents which are also useful as intermediates in the preparation of the 1,2'-di-N-alkyl-4,6-di-O-(aminoglycosyl)-1,3-diaminocyclitols. Preferred compounds of this invention include 1,2'-di-N-ethylsisomicin and 1,6'-di-N-ethylsisomicin.
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- 1-N-alkyl-4,6-di-(aminoglycosyl)-1,3-diaminocyclitols, methods for their manufacture, methods for their use as antibacterial agents, and compositions useful therefor
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1-N-Alkyl-4,6-di-(aminoglycosyl)-1,3-diaminocyclitols, valuable as antibacterial agents, are prepared by treating an acid addition salt of a 4,6-di-(aminoglycosyl)-1,3-diamonocyclitol antibacterial agent in an inert solvent, preferably a protic solvent containing water, with one equivalent of a hydride donor reducing agent and with at least one equivalent of an aldehyde. The 1-N-alkyl-4,6-di-(aminoglycosyl)-1,3-diaminocyclitols are also prepared by treating the corresponding 1-N-acyl-4,6-di-(aminoglycosyl)-1,3-diaminocyclitol with an amide-reducing hydride reagent in an inert organic solvent. Other methods of preparing 1-N-alkyl-4,6-di-(aminoglycosyl)-1,3-diaminocyclitols include carrying out the foregoing processes with partially N-protected intermediates. Another useful process involves preparing a Schiff base of the 1-amino function of a partially N-protected 4,6-di-(aminoglycosyl)-1,3-diaminocyclitol followed by reduction of said Schiff base and removal of the N-protecting groups. Pharmaceutical compositions comprising 1-N-alkyl-4,6-di-(aminoglycosyl)-1,3-diaminocyclitols are described as well as the method of using said compositions to elicit an antibacterial response in a warm blooded animal having a susceptible bacterial infection.
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