- Rate constants for reaction of hydroxyl radicals with sulfapyridine and aminosalicylic acids
-
Sulfasalazine, an anti-inflammatory drug, is metabolized to sulfapyridine and 5-aminosalicylic acid (5-ASA) which is therapeutically active. In the inflammation, active oxygen species have been suggested to play an important role. Among various active oxygen species, hydroxyl radical is known to be the most active radical. To elucidate the reactivity of sulfapyridine, 5- ASA, 4-ASA and 3-ASA with hydroxyl radicals, the rate constants were determined measuring the fluorescence of hydroxybenzoates induced by radiolysis hydroxylation of benzoate. The constant for 5-ASA, strongly fluorescent but insoluble in ether, was measured after ether extraction of hydroxybenzoates under acidic condition. For the other compounds, the rate constants were determined using a method which separates hydroxybenzoates by HPLC after the ether extraction, since the three compounds moved to the ether layer and interfered with the fluorescence of the hydroxybenzoates induced. Four rate constants were obtained in the range of 6.4-7.0 x 109 M-1 s- 1, showing that they similarly scavenge hydroxyl radicals in vitro.
- Motohashi, Noriko,Saito, Yutaka
-
-
Read Online
- Complex Polyheterocycles and the Stereochemical Reassignment of Pileamartine A via Aza-Heck Triggered Aryl C-H Functionalization Cascades
-
Structurally complex benzo- and spiro-fused N-polyheterocycles can be accessed via intramolecular Pd(0)-catalyzed alkene 1,2-aminoarylation reactions. The method uses N-(pentafluorobenzoyloxy)carbamates as the initiating motif, and this allows aza-Heck-type alkene amino-palladation in advance of C-H palladation of the aromatic component. The chemistry is showcased in the first total synthesis of the complex alkaloid (+)-pileamartine A, which has resulted in the reassignment of its absolute stereochemistry.
- Bower, John F.,Caiger, Lewis,García-Cárceles, Javier,Hazelden, Ian R.,Jones, Benjamin T.,Langer, Thomas,Lewis, Richard J.
-
supporting information
p. 15593 - 15598
(2021/10/12)
-
- Synthetic method of methyl salicylate
-
The invention discloses a synthesis method of methyl salicylate. The method comprises the following steps: preparing sodium phenolate by using caustic soda flakes and phenol as raw materials, carryingout carboxylation reaction on the obtained sodium phenolate and carbon dioxide gas to obtain sodium salicylate, reacting the obtained sodium salicylate with chloromethane gas under the action of a phase transfer catalyst to obtain a crude methyl salicylate product containing a toluene solvent, neutralizing and washing the crude methyl salicylate product, recovering the toluene solvent at normal pressure, and carrying out vacuum distillation to obtain a finished methyl salicylate product. According to the method, a strong acid catalyst is not used, so that the wastewater amount is greatly reduced, and the corrosion to equipment and the pollution to the environment are reduced. According to the method, equipment is not seriously corroded, the wastewater amount is small, and the process is more environmentally friendly.
- -
-
Paragraph 0016-0017; 0020-0021; 0024-0025
(2021/02/10)
-
- SAA DERIVATIVE COMPOUND RESTORES ENOS AND INHIBITS OXIDATIVE STRESS-INDUCED DISEASES IN HYPOXIA
-
The Substituted Amine Analogs (SAA) derivative compounds and SAA complex compounds disclosed are characterized as compositions having the functions of inhibiting disorders caused by oxidative stress, and more particularly to those SAA derivative compounds capable of inhibiting disorders caused by oxidative stress consisting of neurodegenerative diseases, lung diseases, oxidative stress-induced heart disease and carvenosus dysfunction.
- -
-
Paragraph 00219; 00220
(2015/11/10)
-
- Evidence of co-operativity in the pre-micellar region in the hydrolytic cleavage of phenyl salicylate in the presence of cationic surfactants of CTAB, TTAB and CPC
-
The effects of cationic surfactants of cetyl trimethyl ammonium bromide (CTAB), tetradecyl trimethyl ammonium bromide (TTAB) and cetyl pyridinium chloride (CPC) on the kinetics of intramolecular general base catalyzed hydrolysis ([OH-] range 0.05-0.1 mol L-1) of phenyl salicylate have been studied at different temperatures. The rate is independent of [OH-] in the studied range. The anionic surfactant sodium dodecyl sulphate (SDS) has no effect on the rate. The presence of small amount of any of these cationic surfactants well below its critical micelle concentration markedly inhibits the rate of reaction suggesting a pre-micellar aggregation between the substrate and surfactant monomers. The kinetic data have been analyzed in terms of earlier reported models (Piszkiewicz's co-operativity model and Raghavan and Srinivasan's model) for micellar catalysis. The binding constants between the substrate and the surfactants evaluated from the two models are in good agreement. Three dimensional structure of the pre-micellar aggregate controls the approach of the nucleophile water molecule to the reaction center. The planar structure of the pyridinium head group of CPC provides less steric hindrance to the attacking water molecule that leads to the least enthalpy of activation for CPC among the three surfactants. The association between the negatively charged substrate and the cationic surfactant is favored owing to electrostatic as well as hydrophobic interactions. The binding between the substrate and pre-micelles follows the order: CPC > TTAB > CTAB.
- Sen, Pratik K.,Chatterjee, Piyali,Pal, Biswajit
-
-
- Growth, shrinking, and breaking of pluronic micelles in the presence of drugs and/or β-cyclodextrin, a study by small-angle neutron scattering and fluorescence spectroscopy
-
The associative structures between F127 Pluronic micelles and four drugs, namely, lidocaine (LD), pentobarbital sodium salt (PB), sodium naproxen (NP), and sodium salicylate (SAL), were studied by small-angle neutron scattering (SANS). Different outcomes for the micellar aggregates are observed, which are dependent on the chemical nature of the drug and the presence of charge or otherwise: the micelles grow with LD, are hardly modified with PB, and decrease in size with both NP and SAL. The partition coefficient, determined by fluorescence spectroscopy, is directly correlated to the amount of charge, following NP ≈ SAL a slightly deeper localization of LD and more superficial for PB. All drugs can form inclusion complexes with heptakis(2,6-di-O-methyl) β-cyclodextrin (hep2,6 β-CD). Hep2,6 β-CD, as shown in previous studies (Joseph, J.; Dreiss, C. A.; Cosgrove, T. Langmuir, 2008, 24, 10005-10010; Dreiss, C. A.; Nwabunwanne, E.; Liu, R.; Brooks, N. J. Soft Matter, 2009, 5, 1888-1896), is also able to form a complex with F127, resulting in micellar breakup. In the ternary mixtures, a fine balance of forces is involved, which results in drastic micellar changes, as observed from the SANS patterns. Depending on the ratio of drug, polymer, and hep2,6 β-CD and the nature of the interactions (which is directly linked to the drug chemical structure), the presence of drug either hinders micellar breakup by β-CD (at high enough concentration of LD or PB) or leads to micellar growth (NP). These effects are mainly attributed to a preferential drug/β-CD interaction (except for PB), which, at least in the conditions studied here, explains the higher β-CD concentration needed for micellar breakup to occur.
- Valero, Margarita,Dreiss, Cecile A.
-
experimental part
p. 10561 - 10571
(2011/01/12)
-
- The improved Kolbe-Schmitt reaction using supercritical carbon dioxide
-
A comparative analysis of the reactions between sodium phenoxide and CO2 under the gaseous and supercritical conditions has demonstrated the preferential effect of supercritical conditions for promoting the reactivity of CO2. A significant increase in product yield was obtained in supercritical CO2 compared to reactions undertaken in gaseous CO2.
- Iijima, Takayuki,Yamaguchi, Tatsuaki
-
p. 5309 - 5311
(2008/02/09)
-
- Regioselective dealkylation of 2-alkoxybenzoic acid and its amide derivatives with aliphatic amines
-
The methoxy group of o-anisic acid was cleaved with aliphatic amines in aprotic dipolar solvents. This cleavage reaction was especially smooth when piperazine in dimethylacetamide was used. This method was applicable to a variety of dealkylations of o-alkoxybenzoic acid and ist amide derivatives with high regio-selectivity.
- Nishioka, Hiroyasu,Nagasawa, Masaaki,Yoshida, Kiyoshi
-
p. 243 - 246
(2007/10/03)
-
- Ion-exchange equilibrium in synthesis of acids on KU-2(H) cation exchanger and of salts on KB-4P-2 cation exchanger
-
Advisability of ion-exchange synthesis of acids on strongly acidic KU-2 cation exchanger and of salts on weakly acidic KB-4P-2 cation exchanger is studied.
- Saidakhmedov,Arslanov,Vulikh
-
p. 211 - 215
(2007/10/03)
-
- Competitive measurement of rate constants for hydroxyl radical reactions using radiolytic hydroxylation of benzoate
-
Hydroxyl radicals were generated from N2O-saturated phosphate-buffered saline solution (pH 7.5) by irradiation with a 3.7 TBq 137Cs source. The radicals attacked benzoate to form highly fluorescent products. The induction of fluorescence was tested in 0.002 to 2 mM of benzoate solution; the fluorescence intensity was approximately constant at benzoate concentrations more than 0.1 mM during irradiation, and increased linearly with irradiation dose up to 53 Gy tested. The major primary products detected by high- performance liquid chromatography were three monohydroxybenzoates, 2-, 3- and 4-hydroxybenzoate (HOBZ). The G-values obtained from γ-irradiation for 60 min of a 0.2 mM benzoate solution were G(2-HOBZ) = 0.97, G(3-HOBZ) = 0.48 and G(4-HOBZ) = 0.45. As the fluorescence of irradiated benzoate solution arose mostly from 2- and 3-HOBZ and the intensity of 2-HOBZ is 30 times that of 3- HOBZ, 98% of the fluorescence intensity induced was ascribed to 2-HOBZ. A hydroxyl radical scavenger competed with benzoate for hydroxyl radicals produced, and diminished the fluorescent products. A rate constant for the reaction of a scavenger with hydroxyl radical could be determined from the reduction in fluorescence intensity, using 0.2 mM benzoate and various concentrations of the scavenger. The fluorescence intensity was detectable down to 0.15 μM of 2-HOBZ produced. For various compounds, rate constants obtained in this way were similar to those measured by pulse-radiolysis.
- Motohashi,Saito
-
p. 1842 - 1845
(2007/10/02)
-
- A New Method for Obtaining Isotopic Fractionation Data at Multiple Sites in Rapidly Exchanging Systems
-
A new method for rapidly and conveniently obtaining isotopic fractionation factors in dilute aqueous solutions of compounds containing rapidly exchanging OH, NH, and SH groups is described.Shifts in the positions of NMR peaks for spectroscopically observable nuclei induced by isotopic substitution are the basis of this procedure which has the unique capability of separately measuring the isotopic exchange constants simultaneously for several different groups in the same molecule.The results for a series of alcohols, amines, thiols, phenols, acids, and amides with use of 13C NMR spectroscopy are reported.Atypically low values of Kfrac are observed in several cases, indicating that there are strong internal hydrogen bonds in competition with those to water, yielding conformational information.
- Jarret, Ronald M.,Saunders, Martin
-
p. 2648 - 2654
(2007/10/02)
-
- Effect of Polyether Linkages on the Carboxylation of Sodium Phenoxide
-
In the carboxylation of sodium phenoxide under mild conditions, the crown compound or polyethers with three to five ether linkages caused carboxylation to give o- and p-hydroxybenzoic acids, but not ethers with one or two linkages.The chelation of sodium phenoxide with polyethers changed the formation ratio of isomers.
- Sakakibara, Tsutomu,Haraguchi, Kazuyo
-
p. 279 - 280
(2007/10/02)
-
