139-85-5Relevant articles and documents
Electrochemically exfoliated graphene for nanosensor applications
Sivasankar,Senthilkumar,Vivekananth,Kalaivani,Sivakumar
, p. 7097 - 7104 (2019)
Water dispersible graphene layer are the excellent nano materials used for wide range of electronic applications. High quality graphene was synthesized by an eco-friendly, easy and cost effective electrochemical exfoliation method. In this work, graphite rod was used both as an anode and cathode for the production of graphene. Potassium sulphate (K2SO4) was used as an intercalating agent. Electrochemically exfoliated graphene (EEG) was coated on glassy carbon electrode (GCE) and evaluated towards the electrochemical oxidation of vanillin and L-phenylalanine. The fabricated electrode was able to detect vanillin and L-Phenylalanine as low as 0.2 μM with signal to noise ratio of 3. A significant increase in the current was observed for the graphene coated electrode for both vanillin and L-phenylalanine when compared to bare Glassy electrode. The finding clearly demonstrated the higher detection capability, selectivity and reproducibility of EEG.
Flavonoids as antioxidants
Jovanovic, Slobodan V.,Steenken, Steen,Tosic, Mihajlo,Marjanovic, Budimir,Simic, Michael G.
, p. 4846 - 4851 (1994)
Spectral, acid-base, and redox properties of the phenoxyl radicals derived from 3,4-dihydroxybenzene derivatives and selected flavonoids were studied by pulse radiolysis of aqueous solutions. From the pH-dependent changes in the phenoxyl spectra, the dissociation constants were derived. The pK(a) values for the deprotonation of the 3'-OH group in the catechin (pK(a) = 4.6) and rutin (pK(a) = 4.3) radicals are similar to the pK(a) value of the 3,4-dihydroxybenzoate radicals, pK(a) = 4.2, which is expected from their similar electronic structures. Deprotonation of 5- and 7-OH in the catechin and rutin and of 5-OH in the hesperidin radicals has no effect on the radical spectra, which is explained by the inefficient coupling of the A-ring of the flavonoid radicals with the unpaired electron. Because of favorable reduction potentials of the phenoxyl radicals, E7 = 0.56-0.7 V vs NHE, flavonoids may act as efficient antioxidants of alkylperoxyl and superoxide/hydroperoxyl radicals. The ac kinetic conductivity method was developed for the measurements of the low reaction rate constants of the superoxide radical reactions with flavonoids and phenols in aqueous solutions at pH 10. The rates of the superoxide radical reactions with flavonoids, k = 3 x 102-5.1 x 104 M-1 s-1, depend on the redox properties and the charge of the flavonoids. The highest rates are measured for the oxidation of quercetin and rutin, whereas the lowest are those for the B-ring monosubstituted derivatives, with substantially higher redox potentials. Uncharged catechin at pH 7 reacts at k = 6.6 x 104 M-1 s-1, whereas the rate at pH 10, where catechin is doubly negatively charged, is approximately 4 times lower, k = 1.8 x 104 M-1 s-1. The activation parameters of the oxidation of rutin and trolox at pH 10 and methylgallate at pH 7 were determined in an attempt to understand why the rates of the superoxide reactions are low despite high driving forces of ΔE ≥ 0.4 V. Low activation enthalpies, ΔH(paragraph) 2.3-3.6 kcal/mol, and negative activation entropies, ΔS(paragraph) = -25-28 cal/(mol K), point to an inner-sphere electron-transfer mechanism.
Stereoselective synthesis of trans-dihydronarciclasine derivatives containing a 1,4-benzodioxane moiety
Varró, Gábor,Pogrányi, Balázs,Grün, Alajos,Simon, András,Heged?s, László,Kádas, István
, p. 2265 - 2285 (2018)
Abstract: Some new trans-dihydronarciclasine derivatives containing a 1,4-benzodioxane moiety were stereoselectively synthesised using our feasible and efficient method developed recently. These new phenanthridone alkaloid analogues were obtained in both racemic and optically active forms. High enantioselectivities (up to 99% ee) were achieved by applying (8S,9S)-9-amino(9-deoxy)epiquinine as an organocatalyst. Due to a side reaction, various methoxyphenanthridine regioisomers were also prepared which afforded further synthetic trans-dihydronarciclasine analogues modified in the ring A of the phenanthridone scaffold. Graphical abstract: [Figure not available: see fulltext.].
Polyoxometalates as solution-phase electrocatalytic mediators for reduced electrode fouling and the improved oxidative response of phenols
Hossain, Md. Mokarrom,Aldous, Leigh
, p. 32 - 35 (2016)
The electrochemical oxidation of phenols typically passivates electrodes, due to the reactive one-electron oxidation intermediate, a phenoxyl radical cation. Here, we show that the addition of polyoxometalates to the electrolyte can prevent electrode passivation via an EC'E mechanism; the initial oxidation is unchanged, but oxidation of the phenoxyl radical intermediate is mediated. As such the electrochemistry assumes an ideal EE process, as confirmed by cyclic voltammetric simulation, with no electrode fouling on the voltammetric timescale. Bulk electrolysis of phenolic molecules can even be performed to isolate solution-phase products. This is exemplified by the scenario of vanillin (phenolic compound) and phosphotungstic acid (H3[PW12O40], a polyoxometalate).
On the difference in decomposition of taxifolin and luteolin vs. fisetin and quercetin in aqueous media
Sokolová, Romana,Rame?ová, ?árka,Kocábová, Jana,Kolivo?ka, Viliam,Degano, Ilaria,Pitzalis, Emanuela
, p. 1375 - 1383 (2016)
Abstract: The decomposition of flavonols quercetin and fisetin, flavone luteolin and flavanone taxifolin was studied in slightly alkaline solution under ambient conditions. The study was based on spectrophotometry and high-pressure liquid chromatography. Products formed by atmospheric oxygen oxidation and hydrolysis were identified by HPLC–DAD and HPLC–ESI-MS/MS. Only small differences in the chemical structure of flavonoids resulted in extremely variable oxidation pathways and products. Oxidation of flavonols led to the formation of both a benzofuranone derivative and several open structures. On the contrary, the benzofuranone derivative was not found as a product of taxifolin and luteolin oxidative decomposition. These compounds were oxidized to their hydroxylated derivatives and typical open structures. Quercetin was not identified as a possible oxidation product of taxifolin. Graphical Abstract: [Figure not available: see fulltext.]
Total synthesis of (±)-fumimycin and analogues for biological evaluation as peptide deformylase inhibitors
Zaghouani, Mehdi,B?geholz, Lena A.K.,Mercier, Evan,Wintermeyer, Wolfgang,Roche, Stéphane P.
, p. 3216 - 3230 (2019)
A concise 7-step total synthesis of (±)-fumimycin in 11.6% overall yield is reported. An acid-catalyzed intramolecular aza-Friedel–Crafts cyclization was developed to construct the benzofuranone skeleton of the natural product bearing an α,α-disubstituted amino acid moiety in a single step. Regioselective chlorination followed by a Suzuki–Miyaura cross-coupling rapidly enabled the preparation of a library of analogues which were evaluated against peptide deformylase for antibacterial activity.
Herbicide based on haloxyfop, flumetsulam and halosulfuron-methyl
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, (2021/06/21)
The invention discloses a herbicide based on haloxyfop, flumetsulam and halosulfuron-methyl. The herbicide is prepared from the following raw materials in parts by weight: 1-15 parts of haloxyfop-R-methyl, 1-15 parts of flumetsulam, 1-37 parts of halosulfuron-methyl, 1-2 parts of a modified antioxidant, 10-12 parts of borax, 6-8 parts of a surfactant, 10-12 parts of triethanolamine, 10-12 parts of vegetable oil and 40-42 parts of deionized water. After the haloxyfop-R-methyl, the flumetsulam and the halosulfuron-methyl are mixed, the effects are complementary, the weeding spectrum is wider, the weeding activity is high, the weeding effect is more excellent. In addition, the modified antioxidant is added into the herbicide formula, so that the composite herbicide has the effects of resisting oxidation aging and ultraviolet aging, effective components are prevented from decomposing and losing efficacy in the presence of light, the pesticide effect is kept lasting, and the application prospect and popularization value are remarkably improved.
A method of synthesis of piperonolamine
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Paragraph 0112; 0116-0118; 0128; 0132-0134, (2022/01/07)
The present invention belongs to the field of organic chemical synthesis, specifically relates to a synthesis method of piperine, comprising: using catechol as a raw material to prepare piperonaldehyde; β - nitro-3,4-dioxenosylstyrene prepared with piperonaldehyde; β - nitro -3,4-dioxenesimethylenestyrene to obtain piperine ethylamine. Among them, the preparation of piperaldehyde from catechol as raw materials includes two ways: (1) catechol→3,4-dihydroxymandelic acid→3,4-dihydroxybenzaldehyde→ piperaldehyde; (2) catechol→ piperine ring → piperine. The raw materials used in the present invention are safe and readily available, low cost; the reaction conditions are mild, the operation is simple, the chemical yield is high, and the intermediate reagents are easy to recover; suitable for industrial production.
A synthetic preparation method for small carbags hydrochloric acid
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Paragraph 0191-0193, (2021/12/08)
The present invention belongs to the field of organic chemistry, relates to a method of synthesizing berberine hydrochloride, comprising: S1: with 5-halo-o-quinoastearaldehyde and piperine ethylamine to obtain N- [2-(3,4-dimethoxyphenyl-5-yl) ethyl] -1- (5-halo-2,3-dimethoxybenzyl) methylimide; S2: to obtain 2- (3,4-diimoxyphenyl) -N- (5-bromo-2,3-dimethoxybenzyl) ethylamine; S3: to obtain 2-(3,4-dimethoxyphenyl) -N- (5-bromo-2 S4: to obtain 12-halogenated berberine derivative; S5: to obtain berberine. The present invention is free from the application of the by-product o-vanillin synthesis of o-resveratal raw material constraints, synthesis of 5- substitute o-resveratal and piperine ethylamine, and the use of the two preparation of berberine hydrochloride, with raw materials readily available, mild reaction conditions, easy to operate, high chemical yield, low cost and other advantages.
Thiols Act as Methyl Traps in the Biocatalytic Demethylation of Guaiacol Derivatives
Grimm, Christopher,Kroutil, Wolfgang,Pompei, Simona,Schiller, Christine,Schober, Lukas
, p. 16906 - 16910 (2021/07/02)
Demethylating methyl phenyl ethers is challenging, especially when the products are catechol derivatives prone to follow-up reactions. For biocatalytic demethylation, monooxygenases have previously been described requiring molecular oxygen which may cause oxidative side reactions. Here we show that such compounds can be demethylated anaerobically by using cobalamin-dependent methyltransferases exploiting thiols like ethyl 3-mercaptopropionate as a methyl trap. Using just two equivalents of this reagent, a broad spectrum of substituted guaiacol derivatives were demethylated, with conversions mostly above 90 %. This strategy was used to prepare the highly valuable antioxidant hydroxytyrosol on a one-gram scale in 97 % isolated yield.
