- Kinetics and mechanism of isatin ring opening in aqueous binary mixtures of methanol and acetonitrile cosolvents
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Solvent effects on the kinetics of hydrolysis of isatin by sodium hydroxide have been investigated within the temperature range (30-55 °C) in methanol-water and acetonitrile-water media of varying solvent compositions up to 70% (v/v) of the organic solven
- Ismail,Zaghloul
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Read Online
- Total synthesis and stereochemistry of uncialamycin
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Unseal the secrets of uncialamycin: The total synthesis of the C26 epimers of the newly discovered enediyne natural product allows its stereochemical assignment and further biological investigations of this potent antibiotic. Key steps involve the additio
- Nicolaou,Zhang, Hongjun,Chen, Jason S.,Crawford, James J.,Pasunoori, Laxman
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- Kinetic spectrophotometric methods for the determination of isatin
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Simple, rapid and sensitive kinetic spectrophotometric methods are described for the analysis of isatin in pure form and in mixture. The procedures were based on the kinetic investigations and studies were done upon the oxidation of isatin with potassium
- Alothman, Zeid A.,Siddiqui, Masoom Raza,Wabaidur, Saikh Mohammad,Al-LOHEDAN, Hamad A.,Ali, Mohd. Sajid,Rafiquee
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- Identification of degradation products of indigoids by tandem mass spectrometry
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The study concerns identification of photodegradation products of indigotin, indirubin and isoindigo. Experimental methodology consists of degradation of standard solutions of indigoids in a solar box and analysis of samples taken at different aging time by using capillary high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometric and spectrophotometric detectors. Identification of the formed compounds was based on careful interpretation of the electrospray ionization MS/MS spectra. Apart from the well-known degradation products of indigoids: isatin, isatoic anhydride and anthranilic acid, another seven species were also identified, and their proposed structures were confirmed by high-resolution molecular masses measurements; according to the best knowledge of authors, they have not been reported so far. The obtained results formed the basis for postulating mechanism of the process. Moreover, the MRM (Multiple Reaction Monitoring) method was developed for the identification of natural dyes and their degradation products in textiles of historical value. Apart from such colorants as indigotin and flavonoids, also presence of degradation products of indigoids was confirmed.
- Witkos?, Katarzyna,Lech, Katarzyna,Jarosz, MacIej
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p. 1245 - 1251
(2015/11/09)
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- Synthesis of 6,7-dihydrodibenzo[b,j]phenanthroline derivatives by pfitzinger condensation of isatin and cyclic diketones
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All two kinds of 6,7-dihydrodibenzo[b,j]phenanthroline derivatives were synthesized by Pfitzinger condensation of isatins with 1,3-cyclohexanedione and 1,4-cyclohexanedione respectively. Structures of the derivatives were confirmed by NMR and other spectr
- Fang, Lizhen,Ma, Jinshuo,Lu, Chenjuan,Li, Huanhuan,Yang, Xiaoli
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p. 209 - 215
(2014/02/14)
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- Improved synthesis of 1-oxo-1,2,3,4-tetrahydroacridine-9-carboxylic acids from isatins and 1,3-cyclohexanedione
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An improved protocol for the preparation of 1-oxo-1,2,3,4- tetrahydroacridine-9-carboxylic acid derivatives via Pfitzinger condensation under acidic conditions is described, it provides a simple one-pot synthetic method for some useful 1-oxo-1,2,3,4-tetra
- Lv, Qinghua,Fang, Lizhen,Lu, Chenjuan,Wang, Pengfei
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experimental part
p. 1457 - 1463
(2012/08/07)
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- Kinetics and reactivity of indole-2,3-dione ring towards alkali in dimethyl sulphoxide-water mixtures
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Kinetics of alkaline hydrolysis of indole-2,3-dione (isatin) and indole-2,3-dione (N-methyl isatin) have been carried out at different percentages of DMSO-H2O mixtures and at different temperatures in the range 30-45°C. The reaction proceeds ac
- Fathalla, Magda F.,Ismail, Amel M.
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p. 901 - 904
(2007/10/03)
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- Kinetics and Thermodynamics of Isatin Ring Opening in Water and Water-Dioxan Mixtures
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The kinetics of amide cleavage of isatin has been studied using sodium hydroxide. The rate of reaction was followed spectrophotometrically within the temperature range (30-45 deg C) in water-dioxan media of varying solvent compositions up to 70 percent (v
- Ismail, A. M.,Harfoush, A. A.,Abdel-Rahman, H. H.
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p. 105 - 115
(2007/10/03)
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- Development of a Novel Biocatalyst for the Resolution of rac-Pantolactone
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A novel L-pantolactone hydrolase, Lph, from Agrobacterium tumefaciens Lu681 was characterized, which stereospecifically hydrolyses L-pantolactone to L-pantoic acid yielding D-pantolactone with > 95% enantiomeric excess. The enzyme was found to be a 30 kDa-Zn2+-hydrolase with a Km for L-pantolactone of 7 mM and a Vmax of 30 U/mg. The corresponding lph gene was identified as an 807 bp ORF and cloned into E. coli. It was overexpressed under control of Ptac and Prha yielding enzyme activities of up to 600 U/g dry weight. Resolution of D,L-pantolactone in repeated batches with isolated Lph and enzyme recovery by membrane filtration gave D-pantolactone with 50% yield and 90-95% ee over 6 days. Covalent immobilization to EupergitC led to a stable biocatalyst easy to handle in a repeated batch production of D-pantolactone. Further improvements in the activity of Lph were achieved by directed evolution of the enzyme. Activities of mutants F62S, K197D and F100L were increased 2.3, 1.7, and 1.5 fold, respectively.
- Kesseler, Maria,Friedrich, Thomas,Hoeffken, Hans Wolfgang,Hauer, Bernhard
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p. 1103 - 1110
(2007/10/03)
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- Effects of Organic Solvents on Indigo Formation by Pseudomonas sp. strain ST-200 Grown with High Levels of Indole
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The indole tolerance level of Pseudomonas sp. strain ST-200 was 0.25 mg/ml. The level was raised to 4 mg/ml when diphenylmethane was added to the medium to 20% by volume. ST-200 grown in this two-phase culture system containing indole (1 mg/ml) and diphenylmethane (0.2 ml/ml) produced a water-soluble yellow pigment, isatic acid, and two water-insoluble and diphenylmethane-soluble pigments, blue indigo and purple indirubin. The amounts of the water-insoluble pigments corresponded to 0.5% (indigo) and 0.2% (indirubin) of the indole added to the medium. Of the conditions tried, indigo and indirubin were formed only when ST-200 was grown in the two-phase system overlaid with organic solvents with appropriate polarity.
- Doukyu, Noriyuki,Arai, Tomonori,Aono, Rikizo
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p. 1075 - 1080
(2007/10/03)
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- The Mechanisms of Hydrolysis of the γ-Lactam Isatin and its Derivatives
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The pH dependences of the rates of hydrolysis of isatin, its N-carboxymethyl derivative and its 5-nitro substituted analogues exhibit a complex behaviour, showing a first- and second-order dependence upon hydroxide ion concentration, as well as a pH-independent pathway.The pH dependence is interpreted in terms of the formation of tetrahedral intermediates in different protonic states which may break down to products via hydroxide ion, hydronium ion and water catalysed pathways.These γ-lactams are as reactive, or more reactive, than benzylpenicillin.
- Casey, Lorraine A.,Galt, Ron,Page, Michael I.
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