- Simple preparation method of 2, 5-dichloropyridine
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The invention provides a green, safe, simple and convenient preparation method of 2, 5-dihydroxybenzene. The method comprises the following steps: by taking maleic acid diester as an initial raw material, carrying out condensation with nitromethane, hydrogenation cyclization and chlorination to prepare 2, 5-dibromobenzene. The preparation method is simple, easy to operate, high in reaction selectivity and high in product yield and purity; The method disclosed by the invention is low in wastewater yield, environment-friendly and high in reaction safety; the used raw materials are cheap and easily available, and the cost is low.
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Paragraph 0048; 0049; 0064; 0065; 0067; 0068; 0070; 0071
(2019/05/16)
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- Mechanism of 6-Hydroxynicotinate 3-Monooxygenase, a Flavin-Dependent Decarboxylative Hydroxylase Involved in Bacterial Nicotinic Acid Degradation
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6-Hydroxynicotinate 3-monooxygenase (NicC) is a Group A FAD-dependent monooxygenase that catalyzes the decarboxylative hydroxylation of 6-hydroxynicotinic acid (6-HNA) to 2,5-dihydroxypyridine (2,5-DHP) with concomitant oxidation of NADH in nicotinic acid degradation by aerobic bacteria. Two mechanisms for the decarboxylative hydroxylation half-reaction have been proposed [Hicks, K., et al. (2016) Biochemistry 55, 3432-3446]. Results with Bordetella bronchiseptica RB50 NicC here show that a homocyclic analogue of 6-HNA, 4-hydroxybenzoic acid (4-HBA), is decarboxylated and hydroxylated by NicC with a 420-fold lower catalytic efficiency than is 6-HNA. The 13(V/K), measured with wild-type NicC by isotope ratio mass spectrometry following the natural abundance of 13C in the CO2 product, is inverse for both 6-HNA (0.9989 ± 0.0002) and 4-HBA (0.9942 ± 0.0004) and becomes negligible (0.9999 ± 0.0004) for 5-chloro-6-HNA, an analogue that is 10-fold more catalytically efficient than 6-HNA. Covalently bound 6-HNA complexes of NicC are not observed by mass spectrometry. Comparative steady-state kinetic and Kd6HNA analyses of active site NicC variants (C202A, H211A, H302A, H47E, Y215F, and Y225F) identify Tyr215 and His47 as critical determinants both of 6-HNA binding (KdY215FKdWT > 240; KdH47EKdWT> 350) and in coupling rates of 2,5-DHP and NAD+ product formation ([2,5-DHP]/[NAD+] = 1.00 (WT), 0.005 (Y215F), and 0.07 (H47E)]. Results of these functional analyses are in accord with an electrophilic aromatic substitution reaction mechanism in which His47-Tyr215 may serve as the general base to catalyze substrate hydroxylation and refine the structural model for substrate binding by NicC.
- Nakamoto, Kent D.,Perkins, Scott W.,Campbell, Ryan G.,Bauerle, Matthew R.,Gerwig, Tyler J.,Gerislioglu, Selim,Wesdemiotis, Chrys,Anderson, Mark A.,Hicks, Katherine A.,Snider, Mark J.
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p. 1751 - 1763
(2019/03/26)
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- Mechanism of the 6-hydroxy-3-succinoyl-pyridine 3-monooxygenase flavoprotein from Pseudomonas putida S16
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6-Hydroxy-3-succinoyl-pyridine (HSP) 3-monooxygenase (HspB), a flavoprotein essential to the pyrrolidine pathway of nicotine degradation, catalyzes pyridine-ring β-hydroxylation, resulting in carbon-carbon cleavage and production of 2,5-dihydroxypyridine. Here, we generated His6-tagged HspB in Escherichia coli, characterized the properties of the recombinant enzyme, and investigated its mechanism of catalysis. In contrast to conclusions reported previously, the second product of the HspB reaction was shown to be succinate, with isotope labeling experiments providing direct evidence that the newly introduced oxygen atom of succinate is derived from H2O. Phylogenetic analysis reveals that HspB is the most closely related to two p-nitrophenol 4-monooxygenases, and the experimental results exhibit thatp-nitrophenol is a substrate of HspB. The reduction of HspB (with maxima at 375 and 460 nm, and a shoulder at 485 nm) by NADH was followed by stopped-flow spectroscopy, and the rate constant for reduction was shown to be stimulated by HSP. Reduced HspB reacts with oxygen to form a C(4a)-(hydro)peroxyflavin intermediate with an absorbance maximum at -400 nm within the first few milliseconds before converting to the oxidized flavoenzyme species. The formed C(4a)-hydroperoxyflavin intermediate reacts with HSP to form an intermediate that hydrolyzes to the products 2,5-dihydroxypyridine and succinate. The investigation on the catalytic mechanism of a flavoprotein pyridine-ring β-position hydroxylase provides useful information for the biosynthesis of pyridine derivatives.
- Yu, Hao,Hausinger, Robert P.,Tang, Hong-Zhi,Xu, Ping
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p. 29158 - 29170
(2015/01/09)
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- Improved syntheses of 5-hydroxy-2-pyridones (2,5-dihydroxypyridines)
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Improved syntheses of 5-hydroxy-2-pyridone, 6-chloro-5-hydroxy-2-pyridone, 2,4-dihydroxynicotinic acid, and three methyl-substituted 5-hydroxy-2-pyridones are reported. Copyright Taylor & Francis Group, LLC.
- Behrman
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p. 1168 - 1175
(2008/09/18)
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- In-situ radiolysis ESR studies of hydroxypyridones
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In situ radiolysis of hydroxypyridones in aqueous solution produces several radicals detected by ESR. These are produced by primary and secondary reactions of hydroxyl radicals. Azaquinoidal structures were detected from 3- and 5-hydroxypyridones.
- Icli, Siddik
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p. 2891 - 2902
(2007/10/02)
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- A Three-Step Synthesis of δ-Aminolaevulinic Acid
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Piperidine-2,5-dione (4) is prepared by catalytic hydrogenation of 5-hydroxy-2-pyridone (3).Ring opening of the lactam 4 with concentrated hydrochloric acid yields the hydrochloride of δ-aminolaevulinic acid (2).
- Herdeis, Claus,Dimmerling, Anna
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p. 304 - 306
(2007/10/02)
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