- N-O Bond Fission as the Rate-Determining Step in the Aqueous Conversion of N-Peptidyl-O-(p-nitrobenzoyl)hydroxylamines to p-Nitrobenzoic Acid and Peptidylhydroxamic Acids
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N-Acetyl-, N-alanyl-alanyl-, N-alanyl-prolyl-, and N-Boc-alanyl-prolyl-O-(p-nitrobenzoyl) hydroxylamines, compounds that are mechanism-based irreversible inactivators of some proteolytic enzymes, are degraded in aqueous buffers at neutral pH to p-nitrobenzoic acid and either the corresponding N-acylhydroxamic acid or products of its further degradation such as the diketopiperazine.At neutral pH, the reactants exist as the monoanion, as a result of the acidity of the -CO-NH-O- linkage.The p-nitrobenzoic acid formed in a mixture of 50percent H2(18)O and 50percent H2(16)O contains less than 2percent (18)O, which shows that nucleophilic attack of water at the ester carbonyl is not occuring in the degradation.The decomposition of the N-alanyl-prolyl derivative, labeled with (15)N at the N-O nitrogen, exhibits a kinetic isotope effect k14/k15 = 1.092 +/- 0.056, suggesting that N-O fission is occuring in the rate-determining step of the degradation.Kinetic solvent isotope effects of 1.02-1.15 are inconsistent with an expectation of factors around 2 or greater for spontaneous hydrolysis of the ester linkage.All derivatives have ΔH* = 24-27 kcal/mol and ΔS* = +4-7 eu, consistent with unimolecular fission of the substrate N-O to generate p-nitrobenzoate ion and the acyl nitrene.The nitrene must suffer nucleophilic attack at nitrogen very rapidly, producing the hydroxamic acid as the initial product.In the peptide derivatives, further reaction to the cyclized products results.
- Demuth, Hans-Ulrich,Fischer, G.,Barth, A.,Schowen, R. L.
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Read Online
- Investigation of structural effects and behaviour of Pseudomonas aeruginosa amidase encapsulated in reversed micelles
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The acetohydroxamic acid synthesis reaction was studied using whole cells, cell-free extract and purified amidase from the strains of Pseudomonas aeruginosa L10 and AI3 entrapped in a reverse micelles system composed of cationic surfactant tetradecyltrimethyl ammonium bromide. The specific activity of amidase, yield of synthesis and storage stability were determined for the reversed micellar system as well as for free amidase in conventional buffer medium. The results have revealed that amidase solutions in the reverse micelles system exhibited a substantial increase in specific activity, yield of synthesis and storage stability. In fact, whole cells from P. aeruginosa L10 and AI3 in reverse micellar medium revealed an increase in specific activity of 9.3- and 13.9-fold, respectively, relatively to the buffer medium. Yields of approximately 92% and 66% of acetohydroxamic acid synthesis were obtained for encapsulated cell free extract from P. aeruginosa L10 and AI3, respectively. On the other hand, the half-life values obtained for the amidase solutions encapsulated in reverse micelles were overall higher than that obtained for the free amidase solution in buffer medium. Half-life values obtained for encapsulated purified amidase from P. aeruginosa strain L10 and encapsulated cell-free extract from P. aeruginosa strain AI3 were of 17.0 and 26.0 days, respectively. As far as the different sources biocatalyst are concerned, the data presented in this work has revealed that the best results, in both storage stability and biocatalytic efficiency, were obtained when encapsulated cell-free extract from P. aeruginosa strain AI3 at w0 of 10 were used. Conformational changes occurring upon encapsulation of both strains enzymes in reverse micelles of TTAB in heptane/octanol were additionally identified by FTIR spectroscopy which clarified the biocatalysts performances.
- Fragoso, Ana,Pacheco, Rita,Karmali, Amin
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Read Online
- Activation and Orientation by Receptor-Substrate Binding. The Case of Acyl Transfer from O-Acetylhydroxylamine
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The strong binding ability of the receptor molecule 1 induces complexation of O-acetylhydroxylamine and of hydroxylamine in their protonated forms; as a result, subsequent reaction of bound CH3COONH3+ becomes fast and selective, giving only acetic acid with a rate enhancement by a factor of about 30.
- Lehn, Jean-Marie,Nishiya, Takako
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Read Online
- Alternating Current Electrolysis as Efficient Tool for the Direct Electrochemical Oxidation of Hydroxamic Acids for Acyl Nitroso Diels–Alder Reactions
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The acyl nitroso Diels–Alder reaction of 1,3-dienes with electrochemically oxidised hydroxamic acids is described. By using alternating current electrolysis, their typical electro-induced decomposition could be suppressed in favour of the 1,2-oxazine cycloaddition products. The reaction was optimised using Design of Experiments (DoE) and a sensitivity test was conducted. A mixture of triethylamine/hexafluoroisopropanol served as supporting electrolyte in dichloromethane, thus giving products of high purity after evaporation of the volatiles without further purification. The optimised reaction conditions were applied to various 1,3-dienes and hydroxamic acids, giving up to 96 % isolated yield.
- F?hrmann, Jan,Hilt, Gerhard
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supporting information
p. 20313 - 20317
(2021/08/12)
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- Novel fluorinated 7-hydroxycoumarin derivatives containing an oxime ether moiety: Design, synthesis, crystal structure and biological evaluation
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A series of fluorinated 7-hydroxycoumarin derivatives containing an oxime ether moiety have been designed, synthesized and evaluated for their antifungal activity. All the target compounds were determined by1H-NMR,13C-NMR, FTIR and HR-MS spectra. The single-crystal structures of compounds 4e, 4h, 5h and 6c were further confirmed using X-ray diffraction. The antifungal activities against Botrytis cinerea (B. cinerea), Alternaria solani (A. solani), Gibberella zeae (G. zeae), Rhizoctorzia solani (R. solani), Colletotrichum orbiculare (C. orbiculare) and Alternaria alternata (A. alternata) were evaluated in vitro. The preliminary bioassays showed that some of the designed compounds displayed the promising antifungal activities against the above tested fungi. Strikingly, the target compounds 5f and 6h exhibited outstanding antifungal activity against B. cinerea at 100 μg/mL, with the corresponding inhibition rates reached 90.1 and 85.0%, which were better than the positive control Osthole (83.6%) and Azoxystrobin (46.5%). The compound 5f was identified as the promising fungicide candidate against B. cinerea with the EC50 values of 5.75 μg/mL, which was obviously better than Osthole (33.20 μg/mL) and Azoxystrobin (64.95 μg/mL). Meanwhile, the compound 5f showed remarkable antifungal activities against R. solani with the EC50 values of 28.96 μg/mL, which was better than Osthole (67.18 μg/mL) and equivalent to Azoxystrobin (21.34 μg/mL). The results provide a significant foundation for the search of novel fluorinated 7-hydroxycoumarin derivatives with good antifungal activity.
- Dai, Peng,Jiao, Jian,Wang, Qing-Qing,Zhang, Shu-Guang,Zhang, Wei-Hua
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- Synthetic method for acetylhydroxylamine
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The invention provides a synthesis method for acetylhydroxylamine. The method adopts a two-step method to synthesize acetylhydroxylamine, a first micro-channel reactor and a second micro-channel reactor are used for replacing a traditional reaction bottle. The complete dissolution concentration of hydroxylamine hydrochloride in water is 42%, and 30% sodium hydroxide solution is prepared. The hydroxylamine hydrochloride aqueous solution and the sodium hydroxide aqueous solution are simultaneously fed into a first micro-channel reactor by using different metering pumps to react, the reaction temperature is controlled to be 20-25 DEG C, reaction liquid is collected, the obtained reaction liquid and ethyl acetate are simultaneously fed into a second micro-channel reactor to react, the reaction temperature is controlled to be 30-35 DEG C, and after the reaction is finished, distilling is conducted to obtain acetylhydroxylamine. The synthetic method of acetylhydroxylamine is improved, the raw materials are simple, the reaction is easy to control, the process is simple, waste is few, the total yield can reach 98%, and the synthetic method is suitable for industrial production.
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Paragraph 0026-0029
(2021/08/06)
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- Hydroxamates as a potent skeleton for the development of metallo-β-lactamase inhibitors
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Bacterial resistance caused by metallo-β-lactamases (MβLs) has become an emerging public health threat, and the development of MβLs inhibitor is an effective way to overcome the resistance. In this study, thirteen novel O-aryloxycarbonyl hydroxamates were constructed and assayed against MβLs. The obtained molecules specifically inhibited imipenemase-1 (IMP-1) and New Delhi metallo-β-lactamase-1, exhibiting an IC50 value in the range of 0.10–18.42 and 0.23–22.33?μM, respectively. The hydroxamate 5 was found to be the most potent inhibitor, with an IC50 of 0.1 and 0.23?μM using meropenem and cefazolin as substrates. ICP-MS analysis showed that 5 did not coordinate to the Zn(II) ions at the active site of IMP-1, while the rapid dilution, thermal shift and MALDI-TOF assays revealed that the hydroxamate formed a covalent bond with the enzyme. Cytotoxicity assays indicated that the hydroxamates have low toxicity in MCF-7 cells. This work provided a potent scaffold for the development of MβLs inhibitors.
- Chen, Cheng,Chigan, Jia-Zhu,Ding, Huan-Huan,Li, Jia-Qi,Liu, Lu,Xu, Yin-Sui,Yang, Ke-Wu
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- Co(III)-Catalyzed C-H Amidation of Nitrogen-Containing Heterocycles with Dioxazolones under Mild Conditions
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A cobalt(III)-catalyzed C-8 selective C-H amidation of quinoline N-oxide using dioxazolone as an amidating reagent under mild conditions is disclosed. The reaction proceeds efficiently with excellent functional group compatibility. The utility of the current method is demonstrated by gram scale synthesis of C-8 amide quinoline N-oxide and by converting this amidated product into functionalized quinolines. Furthermore, the developed catalytic method is also applicable for C-7 amidation of N-pyrimidylindolines and ortho-amidation of benzamides.
- Dhiman, Ankit Kumar,Thakur, Ankita,Kumar, Inder,Kumar, Rakesh,Sharma, Upendra
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p. 9244 - 9254
(2020/08/14)
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- Rhodium(III)-catalyzed C4-amidation of indole-oximes with dioxazolones: Via C-H activation
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A novel method for the Rh(III)-catalyzed oxime-directed C-H amidation of indoles with dioxazolones has been developed. This strategy provides an exclusive site selectivity and the directing group can be easily removed. This transformation features a wide substrate scope, good functional group tolerance and excellent yields, and may serve as a significant tool to construct structurally diverse indole derivatives for the screening of potential pharmaceuticals in the future. This journal is
- Deng, Ke-Zuan,Fu, Xiao-Pan,Ji, Ya-Fei,Tang, Shi-Biao,Wu, Gao-Rong,Xia, Cheng-Cai,Yang, Jin-Yue,Zhang, Li-Li
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supporting information
p. 7922 - 7931
(2020/11/02)
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- Design, synthesis and evaluation of wound healing activity for β-sitosterols derivatives as potent Na+/K+-ATPase inhibitors
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β-Sitosterols, is a common steroid that can be identified in a variety of plants and their efficacy in promoting wound healing has been demonstrated. Na+/K+-ATPase, more than a pump, its signal transduction function for involvement in cell growth regulation attracts widespread concern. The Na+/K+-ATPase/Src receptor complex can serve as a receptor involved in multiple signaling pathways including promoting wound healing pathways. To finding potent accelerating wound healing small molecular, we choose the high inhibitory activity of Na+/K+-ATPase and non-cardiotoxic natural compound, β-sitosterol as the substrate. A series of β-sitosterol derivatives were designed, synthesized and evaluated as potential Na+/K+-ATPase inhibitors. Among them, compounds 31, 47, 49, showed improved inhibitory activity on Na+/K+-ATPase, with IC50 value of 3.0 μM, 3.4 μM, 2.2 μM, which are more potent than β-sitosterol with IC50 7.6 μM. Especially, compound 49 can induce cell proliferation, migration and soluble collagen production in L929 fibroblasts. Compared to model, compound 49 can accelerate wound healing in SD rats. Further studies indicated that 49 can activate the sarcoma (Src), uptake the protein kinase B (Akt), extracellular signal-regulated kinase (ERK) proteins expression in a concentration dependent manner. Finally, binding mode of compound 49 with Na+/K+-ATPase was studied, which provides insights into the determinants of potency and selectivity. These results proved β-stitosterol derivative 49 can serve as an effective inhibitor of Na+/K+-ATPase and potential candidate for accelerating wound healing agents.
- Cui, Shaoyu,Jiang, Hongli,Chen, Lei,Xu, Jian,Sun, Wenzhuo,Sun, Haopeng,Xie, Zijian,Xu, Yunhui,Yang, Fubai,Liu, Wenyuan,Feng, Feng,Qu, Wei
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- Experimental and computational studies on hydroxamic acids as environmental friendly chelating corrosion inhibitors for mild steel in aqueous acidic medium
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In the present study, three hydroxamic acids (HAs) namely acetohydroxamic acid (AHA), benzohydroxamic acid (BHA) and oxalohydroxamic acid (OHA) were synthesized, characterized and used as inhibitors for mild steel corrosion in1 M HCl using chemical, electrochemical, surface and computational methods. Results of the studies show that the HAs act as effective corrosion inhibitors and their inhibition efficiencies follow the order: OHA (96.37%) > BHA (95.69%) > AHA (93.29%). EIS study showed that studied HAs act as interface type inhibitors. Polarization study revealed that HAs demonstrate mixed-type corrosion inhibitors characteristics and adsorb on the active sites of metallic surface. Adsorption of HAs on metal-1 M HCl interfaces followed the Langmuir adsorption isotherm model. Surface morphological analyses of inhibited and uninhibited metallic surface were carried out using SEM-EDX and XRD methods. DFT analyses showed that studied compounds act as chelating type of ligands. Effect of Keto-enol tautomerism and different possible conformational isomers on metallic corrosion inhibition was demonstrated. The conformational isomers in which >C=O and –OH (hydroxyl) groups present in same side behave as chelating ligands and form relatively more stable complex than that of conformational isomers in which >C=O and –OH groups present in opposite side. Experimental and DFT studies complimented each other well.
- Al Fantazi, Akram,Asatkar, Ashish,Ebenso, Eno E.,Hussain, Chaudhery Mustansar,Khan, Fahmida,Verma, Chandrabhan,Verma, Dakeshwar Kumar
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- Synthesis of benzothiadiazine-1-oxides by rhodium-catalyzed C-H amidation/cyclization
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A rhodium-catalyzed C-H amidation/cyclization sequence provides benzothiadiazine-1-oxides from sulfoximines and 1,4,2-dioxazol-5-ones in good yields. The reaction is characterized by a high functional group tolerance and, in contrast to most previous transformations of this type, is well-suited for S-alkyl-S-arylsubstituted sulfoximines.
- Bolm, Carsten,Kong, Deshen,Ma, Ding,Shi, Peng,Tu, Yongliang,Wang, Chenyang
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supporting information
p. 8842 - 8845
(2020/11/30)
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- Synthesis method of urease inhibitor acetohydroxamic acid
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The invention relates to the field of animal husbandry additive preparation, in particular to a synthesis method of a urease inhibitor acetohydroxamic acid. The method comprises the following steps: reacting hydroxylamine hydrochloride with ethyl acetate in an alkaline solvent system, and performing extraction by using an organic solvent after the reaction is finished, with the chemical equation being CH3COOC2H5 + NH2OH.HCl -> CH3CONHOH. The synthesis method can realize industrial mass production of the acetohydroxamic acid, and can ensure a high yield and high purity of the acetohydroxamic acid. The solvents used in the production process can be recycled, and the preparation method is green and economical.
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Paragraph 0023-0061
(2019/12/02)
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- Sterol derivatives and its preparation method and application
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The invention discloses a sterol derivative of beta-sitosterol, beta-stigmasterol and cholesterol, and is shown as a formula VI. The invention also discloses a preparation method of the sterol derivative. The invention also discloses application of the sterol derivative to the aspect of preparation of wound healing promoting medicine. By starting from easily obtained natural products, the beta-sitosterol, the beta-stigmasterol and the cholesterol are used as starting raw materials; the synthetic method is simple; better operability and reaction yield are realized. The prepared sterol derivative has the obvious wound healing promoting activity; the multiplication, migration and collagen synthesis capability on L929 mechanocytes is obviously higher than that of the raw material and positive control medicine recombinant human bFGF (basic fibroblast growth factor). Compared with protide type medicine (such as bFGF), the prepared sterol derivative has more diversified dosage forms and medication modes; the reference is provided for the application in the field of wound healing promoting. The formula VI is shown as the accompanying diagram.
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Page/Page column 12-30
(2019/05/19)
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- Experimental and computational studies on H2O-promoted, Rh-catalyzed transient-ligand-free ortho-C(sp2)-H amidation of benzaldehydes with dioxazolones
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An efficient and convenient ligand-free, rhodium-catalyzed ortho-C(sp2)-H amidation of benzaldehydes with dioxazolones using H2O as the key promoter is described. Using this protocol, a wide range of benzaldehyde substrates were selectively amidated in good to excellent yields with broad functional group compatibility. KIE experiments revealed that the C-H bond activation was likely the rate-limiting step. In addition, computational studies indicated that the catalyst precursor interacted with water and dioxazolones to generate the active catalytic species. Notably, the practicality and efficacy of this method were illustrated by a late-stage amidation of an estrone-derived molecule and further transformations of the amidated product.
- Ding, Jun,Jiang, Wei,Bai, He-Yuan,Ding, Tong-Mei,Gao, Dafang,Bao, Xiaoguang,Zhang, Shu-Yu
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supporting information
p. 8889 - 8892
(2018/08/17)
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- A method for synthesis of acetyl iodo phenylamino (by machine translation)
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The invention relates to a method for synthesis of acetyl iodo phenylamino, the method to hydroxylamine sulfate and ethyl acetate as raw materials, in order to sodium ethoxide ethanol solution is catalyst, iodo phenylamino synthesis of acetyl, with traditional synthetic method (such as sodium hydroxide as catalyst) compared with the, process is simple, easily available raw materials, raw materials are the large chemical raw materials, low cost, high yield, easy to popularize industrially. (by machine translation)
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Paragraph 0043-0044
(2017/05/26)
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- Synthesis and biological activity of salinomycin-hydroxamic acid conjugates
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Several salinomycin-hydroxamic acid conjugates were designed and synthesized. Most conjugates showed better antiproliferative activities than salinomycin in HT-29 colon cancer, HGC-27 gastric cancer, and especially in MDA-MB-231 triple-negative human breast cancer cells. These conjugates are stable in cell culture media, and they showed much better biological activities than the 1:1 physical mixture with hydroxamic acids and salinomycin. The better membrane permeability and hydrolysis rate of the conjugates may lead to the activity improvements.
- Li, Bo,Wu, Jun,Zhang, Wenxuan,Li, Zhongwen,Chen, Gang,Zhou, Qi,Wu, Song
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p. 1624 - 1626
(2017/03/16)
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- Synthesis of 2,4-dinitrobenzene oxygen amine method
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The invention discloses a method for synthesizing 2,4-dinitrobenzene oxygen amine. The method comprises the following steps: adding hydroxylammonium salt, water and acetic ester into a reaction vessel according to the ratio of n (acetic ester): n (hydroxylammonium salt) being 1.0-2.0:1, dropwise adding 30% alkali metal hydroxide aqueous solution at 15-40 DEG C and continuously reacting for 1 hour according to the ratio of n (alkali metal hydroxide): n (hydroxylammonium salt) being 1.5-3; heating up to 50 DEG C after the reaction, dropwise adding an acetic ester solution of 2,4-dinitrochlorobenzene (at the concentration of 50%) according to the ratio of n (2,4-dinitrochlorobenzene): n (hydroxylammonium salt) being 0.5-1.0, and continuously reacting for 2 hours after dropwise adding; cooling, filtering, beating and washing with alkali lye; adding filter cake into the reaction vessel, adding equimolar hydrochloric acid, heating up and reacting for 1-3 hours, cooling and filtering; and recrystallizing the filter cake with methanol so as to obtain the product. According to the invention, reaction steps are short; raw materials are cheap and easily available; operation is simple; and the method is easy for industrial production.
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Paragraph 0033; 0034
(2016/12/22)
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- Production of hydroxamic acids by immobilized Pseudomonas aeruginosa cells: Kinetic analysis in reverse micelles
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Intact cells from Pseudomonas aeruginosa strain L10 containing amidase were used as biocatalysts both free and immobilized in a reverse micellar system. The apparent kinetic constants for the transamidation reaction in hydroxamic acids synthesis, were determined using substrates such as aliphatic, amino acid and aromatic amides and esters, in both media. In reverse micelles, K m values decreased 2-7 fold relatively to the free biocatalyst using as substrates acetamide, acrylamide, propionamide and glycinamide ethyl ester. We have concluded that overall the affinity of the biocatalyst to each substrate increases when reactions are performed in the reversed micellar system as opposed to the buffer system. The immobilized biocatalyst in general, exhibits higher stability and faster rates of reactions at lower substrates concentration relatively to the free form, which is advantageous. Additionally, the immobilization revealed to be suitable for obtaining the highest yields of hydroxamic acids derivatives, in some cases higher than 80%.
- Bernardo, Marisa,Pacheco, Rita,Serralheiro, Maria Luisa M.,Karmali, Amin
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- Transamidation of primary amides with amines using hydroxylamine hydrochloride as an inorganic catalyst
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Metal-free catalysis: A method for the transamidation of primary amides with primary or secondary amines provides access to secondary and tertiary amides, by utilizing catalytic quantities of hydroxylamine hydrochloride to activate the chemically robust primary amide group (see scheme). A mechanism of primary amide activation through a hydrogen-bonding complex is proposed. Copyright
- Allen, C. Liana,Atkinson, Benjamin N.,Williams, Jonathan M. J.
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supporting information; experimental part
p. 1383 - 1386
(2012/04/18)
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- The reaction of hydroxylamine with aspirin
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Hydroxylamine reacts with aspirin in aqueous solution at 25 °C predominantly through oxygen, to give O-acetylhydroxylamine as the initial product (Scheme 3). The reaction is much faster than the intramolecular general base catalysed hydrolysis of the carboxylate anion, as it is also for the CO2H form of aspirin. Both reactions are faster than expected, consistent with moderate activation and/or proton transfer catalysis of hydroxylaminolysis by both CO2- and CO2H groups. Calculations support oxygen attack as the preferred reaction, but do not permit a clear choice between mechanisms involving NH2OH and +NH3-O- as the effective nucleophile. ARKAT-USA, Inc.
- Medeiros, Michelle,Souza, Bruno S.,Orth, Elisa S.,Brandao, Tiago A. S.,Rocha, Willian,Kirby, Anthony J.,Nome, Faruk
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scheme or table
p. 461 - 476
(2011/10/05)
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- Flash vacuum pyrolysis of 1,2,5-oxadiazole 2-oxides and 1,2,3-triazole 1-oxides
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The flash vacuum pyrolysis (FVP, 450-600 °C/10-3 mmHg) of 3,4-diaryl- and 3,4-dialkyl-1,2,5-oxadiazole 2-oxides (furoxans) has been investigated. In all cases the 1,2,5-oxadiazole ring cleaved cleanly at O(1)-N(2) and C(3)-C(4) to afford two nitrile oxide fragments, which were trapped in high yield (75-97%) as their isoxazoline cycloadducts by reaction with alk-1-enes. At higher temperatures (700-800 °C) isocyanates were formed as by-products. The dimerisation of acetonitrile oxide to dimethylfuroxan was followed by 1H NMR spectroscopy, and the rate constant for the 2 nd order reaction determined. The furoxans were converted into isocyanates in good yield (61-95%) by FVP, followed by sulfur dioxide-mediated isomerisation of the resulting nitrile oxides. 2,4,5-Trisubstituted-1,2,3- triazole 1-oxides showed greater thermal stability, but at 700-800 °C decomposition of the 4,5-dimethyl compound 25b lead to 1,2-di(5-methyl-2-phenyl- 1,2,3-triazol-2-yl)ethane as the major product; attempts to trap acetonitrile oxide were unsuccessful. ARKAT USA, Inc.
- Mitchell, William R.,Paton, R. Michael
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experimental part
p. 34 - 54
(2011/02/21)
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- PROCESS FOR PRODUCING CYCLIC N-HYDROXYIMIDE COMPOUND
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A cyclic polycarboxylic acid anhydride, a polycarboxylic acid, or a mixture of them is allowed to react with hydroxylamine or a salt thereof in an organic solvent under dewatering conditions to yield a corresponding cyclic N-hydroxyimide compound. The cyclic polycarboxylic acid anhydride can be, for example, succinic anhydride or glutaric anhydride. The polycarboxylic acid can be, for example, succinic acid, glutaric acid, or adipic acid. In this process, the reaction is preferably carried out using an organic solvent capable of undergoing azeotropy with water as all or part of a reaction solvent while removing water from the reaction system by azeotropy with the organic solvent. This process produces a cyclic N-hydroxyimide compound in a good yield from any of a cyclic polycarboxylic acid anhydride and a polycarboxylic acid.
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Page/Page column 16-17
(2008/06/13)
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- Metal-catalyzed hydroxylaminolysis of unactivated amide and peptide bonds.
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Kinetics of the hydroxylaminolysis of acetamide, glycinamide, glycylglycine and triglycine have been studied in the range of temperatures 37-60 degrees C as a function of pH and hydroxylamine concentration. Rate constants for specific acid, general-acid and general-base catalyzed pathways have been determined for all substrates (for glycine derivatives rate constants for different protonation forms were obtained). Testing different metal ions as possible reaction catalysts revealed a significant catalytic effect of Zn(II) on the hydroxylaminolysis of glycine substrates, but not acetamide. On the basis of the kinetic results, a mechanism of Zn(II) catalysis is proposed, which involves the coordination of the metal ion to the alpha-amino group of the substrate and the base-assisted nucleophilic attack of hydroxylamine on the bound substrate. The product analysis by proton NMR shows that the primary reaction product in the catalytic reaction is glycine hydroxamic acid, which undergoes further Zn(II)-catalyzed hydrolysis to glycine. Thus the final result of the Zn(II)-catalyzed treatment of peptides by hydroxylamine is hydrolytic cleavage.
- Gomez-Reyes, Baldomero,Yatsimirsky, Anatoly K
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p. 866 - 872
(2007/10/03)
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- Protective solutions for organs
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Described is a protective solution for avoiding ischemic, storage or ischemia/reperfusion to organs, or to isolated cell systems, or to tissue components after perfusion, surgery, transplantation, or cryopreservation and subsequent reperfusion, which contains alkali ions, and if need be also alkaline earth ions as the electrolyte, a buffer e.g. on a histidine derivation basis, as well as a polyol and/or a saccharide, has an osmolarity of about 290 mosm/l to about 350 mosm/l, as well as a pH value of about 6.8 to about 7.4, and to which hydroxamic acid, and/or one or more hydroxamic acid derivatives are added.
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- Linear Bronsted-type behavior in the aminolysis of substituted naphthyl acetates
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The reactions of 4-acetyl-1-naphthyl acetate (1) and 6-acetyl-2-naphthyl acetate (2) with a series of amines of varying pKa, viz. morpholine, ammonia, ethanolamine, glycine, n-butylamine, piperidine, hydrazine, imidazole, and hydroxylamine, are subjected to a kinetic investigation in aqueous medium, 30 °C, ionic strength 0.1 M (KCl). Pseudo-first-order rate coefficients (kobs) are found under amine excess. The plots of (kobs-kH) against free amine concentration are linear at constant pH. The macroscopic nucleophilic substitution rate coefficients (kN) are obtained as the slopes of these plots and found to be pH-independent for all the amines employed. The Bronsted-type plots obtained (log kN against amine pKa) for the aminolysis of both esters 1 and 2 are linear with slope values of β = 0.74 and β = 0.94, respectively. From these values, the kinetic law and the analysis of products, it is deduced that for both esters aminolysis proceed through a zwitterionic tetrahedral addition intermediate (T±) whereby its dissociation into products is rate-limiting (k2 step). Comparison of kN values among them shows that both esters follow an identical mechanistic pathway with 1 having higher reactivity than 2, the reasons for which are discussed.
- Rajarathnam,Ananthakrishna Nadar
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p. 157 - 164
(2007/10/03)
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- The Use of N,O-bis(tert-Butoxycarbonyl)-hydroxylamine in the Synthesis of N-Hydroxylamines and Hydroxamic Acids
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N,O-bis(tert-butoxycarbonyl)-hydroxylamine has been used in the synthesis of 5-lipoxygenase inhibitor LY280810.In addition, this reagent utilized to synthesize a number of other hydroxylamine and hydroxamic acid derivatives in high yields.
- Staszak, Michael A.,Doecke, Christopher W.
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p. 6021 - 6024
(2007/10/02)
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- SUBSTITUTED 3,4-DIHYDRONAPHTHALENES, PHARMACEUTICAL COMPOSITIONS CONTAINING THEM, AND PREPARATION PROCESSES
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Substituted 3,4-dihydronaphthalenes of the formula I wherein R1 is a methyl or an amino group, R2 represents a hydrogen atom or a methyl group, and R3 is a linear or branched chain alkyl residue having 1 to 4 carbon atoms, an allyl or a crotyl group or a cyclopentyl group are disclosed which specifically inhibit 5-lipoxygenase and are useful in pharmaceutical compositions for prophylaxis and treatment of disorders attributable to the action of leucotrienes. The dihydronaphthalenes may be prepared by reacting a compound of formula II. with hydroxylamine or a salt thereof to form the corresponding oxime, reducing the oxime to a hydroxylamine of formula III and introducing a -CO-R1 group.
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- Peroxygen bleach activators and bleaching compositions
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The present invention relates to N,O-diacyl,N-acyl hydroxylamines and their use as bleach activators in conjunction with oxygen-releasing compounds.
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- Mechanism of Reaction of Isomeric Nitrolic Acids to Nitrile Oxides in Aqueous Solution
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Both E and Z isomers of acetonitrolic acids 15 and 16 can be prepared when the OH group is protected by acetylation.Photoisomerization of the E-isomer resulted in quantitative conversion into the pure Z-isomer 16.Hydrolysis of the E-isomer 15 produced the parent nitrolic acid 14 which undergoes loss of NO2(1-) from the conjugate base at high pH.This reaction is however relatively slow suggesting base solubility and acidic reprecipitation as a method of purification of E-nitrolic acids.Deprotection of (Z)-O-acetylacetonitrolic acid by HO(1-) gives a highly reactive Z-nitrolic acid 17 which undergoes loss of NO2(1-) at a rate which precludes its detection; however the subsequent reactions of acetonitrile oxide (CH3CNO) formed were monitored.Rapid loss of NO2(1-) therefore occurs when there is assistance from an antiperiplanar lone pair on the imino nitrogen of the oximate anion.Arylnitrolic acids were also examined; these were in the E configuration 26 and therefore underwent slow loss of NO2(1-).Since NMR and IR data are unreliable for the assignment of configuration of nitrolic acids (relative to other oximes) a single crystal diffraction study was carried out on E-acetonitrolic acid 14.The large difference in reactivity observed for the E- and Z-nitrolic acids now permits strong supporting evidence for structural assignments.
- Egan, Carmel,Clery, Maurice,Hegarty, Anthony F.,Welch, Alan J.
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p. 249 - 256
(2007/10/02)
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- 14N Quadrupole Double Resonance in Some Substituted Hydroxamic Acids
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14N quadrupole coupling constants and asymmetry parameters have been measured in a number of hydroxamic acids by double-resonance field-cycling techniques based on either irradiation in zero magnetic field or cross relaxation.The compounds all display high asymmetry parameters.Those in which this quantity is greater than 0.9 show remarkable line shapes for the two lower 14N frequencies (νy, νz) in their irradiation spectra.They are explained in terms of a thermal-mixing mechanism, which generates polarization of the 1H dipolar levels when these nearly degenerate frequencies are strongly irradiated in zero field, and then subsequently modified by level crossing when the sample is returned to high field to measure the remaining 1H signal.Ab initio SCF-MO calculations of the 14N quadrupole tensor in a group of molecules at the orientation found in crystals of acetohydroxamic acid hemihydrate and oxalodihydroxamic acid are in reasonable agreement with experiment and predict that in all the hydroxamic acids studied the maximum principal component is negative and closely parallel to the direction of the 2p? orbital.
- Ruiqin, Wang,Xiaolan, Yu,Zhenye, Feng,Haq, Mian M. I.,Khurshid, Muhammed M. P.,et al.
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p. 114 - 120
(2007/10/02)
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- cis-trans Isomerism in Monoalkylhydroxamic Acids by 1H, 13C and 15N NMR spectroscopy
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The first example of cis-trans isomerism in monoalkylhydroxamic acids, detected by 1H, 13C and 15N NMR spectroscopy, is reported.The 15N NMR spectrum of CH3CO(15)NHOH gave a clear assignment of the OH and NH protons of both Z and E isomers.The assignment was confirmed by 1H and 13C NMR spectroscopy.A rotational barrier of isomerization (ΔG++c) of 17.8 kcal mol -1 was calculated from the variable-temperature 1H NMR spectra using the method of Shanan-Atidi and Bar-Eli.KEY WORDS cis-trans Isomerism 1H, 13C and 15N NMR Monoalkylhydroxamic acids Rotational barrier
- Brown, David A.,Glass, William K.,Mageswaran, Rajeswary,Girmay, Berhane
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p. 970 - 973
(2007/10/02)
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- A Study of the Mechanism of the Reactions Catalyzed by the Amidase Brevibacterium sp. R312
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Besides its amide hyrolase activity, the amidase from Brevibacterium sp.R312 also exhibits an acyl-transferase activity.The mechanism of the transfer reaction of the acyl from acetamide to hydroxylamine was studied.This is a "Bi Bi Ping Pong" type reaction.The kinetic parameters of the reaction were determined: -Apparent Vm = 135 μmol min-1 mg-1 -Acetamide Km = 18.2 mM -hydroxylamine Km = 131 mM A reaction mechanism involving the -SH group of the amidase was proposed.
- Maestracci, Marc,Thiery, Alain,Arnaud, Alain,Galzy, Pierre
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p. 2237 - 2242
(2007/10/02)
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- Nucleophilic Reactivity toward Acetyl Chloride in Water
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Rate constant ratios for the reactions of acetyl chloride with nucleophilic reagents in water containing 2.5percent (v/v) dioxane were determined by product analysis.The rate constants show a small dependence on the basicity of primary amines, with βnuc=0.25, and are assigned to rate-limiting attack of the nucleophile.Pyridines with pKa>5 behave similarly, with βnuc=0.24, but less basic pyridines react more slowly.Several "α-effect" amines and anionic oxygen nucleophiles show small rate enhancements that are attributed to increases in the rate of nucleophilic attack.The rate constants do not fit the N+ correlation equation, and it is concluded that the reactions of nucleophilic reagents with acyl compounds are not satisfactorily correlated by simple modifications of this equation.
- Palling, David J.,Jencks, William P.
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p. 4869 - 4876
(2007/10/02)
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- A FACILE PREPARATION OF ALIPHATIC HYDROXAMIC ACID FROM N,N,O-TRIS(TRIMETHYLSILYL)HYDROXYLAMINE AND ACID CHLORIDE
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N,N,O-Tris(trimethylsilyl)hydroxylamine reacts readily with various aliphatic acid chlorides under mild conditions to afford the corresponding hydroxamic acids in good yields.
- Ando, Wataru,Tsumaki, Hidetoshi
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p. 1053 - 1056
(2007/10/02)
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- Nuclear magnetic resonance study of addition-cyclization involving ethyl thioacetoacetate and α-nucleophiles
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Addition of NH2NH2 or NH2OH to ethyl thioacetoacetate to form the corresponding cyclic product, 3-methylpyrazol-5-one or 3-methylisoxazol-5-one proceeds via cyclization of the carbinolamine formed by addition to the β-keto carbon, i.e., cyclization is faster than dehydration of the carbinolamine to form the imine.In contrast the corresponding carbinolamine derived from ethylacetoacetate undergoes dehydration faster than cyclization.By means of 1H nuclear magnetic resonance spectroscopy, it is possible to detect the cyclic carbinolamine as well as another transient and measure their rates of decay.Based on these results, a mechanism is proposed.
- Cocivera, Michael,Basu, Soumen,Copp, Leslie,Malatesta, Vincenzo
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p. 629 - 634
(2007/10/02)
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- SUR LA REACTION ENTRE LE CHLORURE DE PYRIDINIUM ET LES NITROALCANES PRIMAIRES
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The lack of homogeneity in the dealkylation of phenol ethers by pyridinium halides had been overcome in a few cases by the use of solvents such as quinoline.The high dissolving power of nitrohydrocarbons led us to study their behaviour in the presence of pyridinium chloride and of 2-methoxynaphthalene 1, taken as the reference ether.On one hand, nitrobenzene is a good solvent which homogenizes the reaction mixture but slows down the reaction; on the other hand, it is not so with nitroalkanes which quickly interact.Thus, a mixture of 2-methoxynaphthalene 1, nitroethane and pyridinium chloride yields, after refluxing, 1-chloro-2-methoxynaphthalene 2, 1-acetylpyridinium chloride oxime 3, acetic acid, acetohydroxamic acid 5, acetonitrile, acetamide and ammonium chloride, in various proportions according to the relative amounts of reagents or the heating duration.The unusual chlorination of 1 can be carried out with primary nitro-alkanes other than nitroethane.Methyl phenol ethers other than 1 can be halogenated if they have a sufficiently electrophilic position.With this method, we were able to synthesize a few mono- or dichlorinated compounds starting from 1,6- or 1,7-dimethoxynaphthalenes and 5-methoxybenzofuran.The study of the experiments run with varying proportions of reactants or with overaddition of one or the other of the resulting products suggests a few mechanisms.Pyridinium bromide induces the same type of reaction, but with lower yields.
- Dauzonne, Daniel,Demerseman, Pierre,Royer, Rene
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p. 601 - 608
(2007/10/02)
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- Nonenzymatic Catalysis by Metal Ions and Phosporic Acid Esters of Hydroxamic Acid Formation
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Nonenzymatic Catalysis by bivalent ions of Be, Mg, Ca, Zn, Mn, Ni and Co and bioorganic phosphates of the formation of hydroxamic acids from acetate or amino acids has been studied systematically.Increased yields of hydroxamate were observed at particular combinations of reactants.The most prominent increase (ca. 15-fold) was found with acetate and Ni++, and with a combination of ATP and Be++.Among others especially ribose-5-phosphate and glucose-5-phosphate enhanced yields in the presence of most metal ions.Since no release of inorganic phosphate was observed, this effect cannot be interpreted as an evidence for intermediate transphosphorylation reactions; it may also result from simple catalytic effects of metal sugar complexes. - Keywords: Prebiological Evolution, Bioids, Transphosphorylation, Hydroxylamine, Acylate Activation
- Saygin, Oemer,Decker, Peter
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p. 727 - 730
(2007/10/02)
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- Novel hydroxamic acid derivatives and medicaments for treatment of urolithiasis and pyelonephrosis comprising such derivatives
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A novel compound having the general formula: STR1 wherein R1 is a residual group selected from the group consisting of substituted phenyl, carbonoylaminophenyl and heterocyclic groups, and R2 is hydrogen or methyl group, and its salts of a pharmacologically acceptable base and a novel medicament containing the compound or its salt mentioned above as a principal component; and the compound and the salt thereof having superior effect for the treatment of urolithiasis and the pyelonephrosis by exhibiting a strong urease inhibitory action, a high transfer rate into the urine and a low toxicity.
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