- TARAXACOSIDE, A TYPE OF ACYLATED γ-BUTYROLACTONE GLYCOSIDE FROM TARAXACUM OFFICINALE
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Key Word Index - Taraxacum officinale; Compositae; Chichoriaceae; roots; lactone glycoside; butyrolactone acylglycoside; glucose ester; p-hydroxyphenylacetic acid; taraxacoside; β-O--β-hydroxy-γ-butyrolactone. - In addition to the four new sesquiterpene lactones previously identified, a new acylated γ-butyrolactone glucoside, taraxacoside, was isolated from the roots of Taraxacum officinale.Its structure was elucidated mainly by 1H and 13C NMR studies as β-O--β-hydroxy-γ-butyrolactone.This seems to be the first instance of the detection of a monocyclic five-membered, saturated lactone O-glycoside.Additionally, p-hydroxyphenylacetic acid was identified for the first time as an acylating acid in a sugar ester.
- Rauwald, Hans-Willi,Huangs, Jai-Tung
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- In Situ Electrochemical Monitoring of Caged Compound Photochemistry: An Internal Actinometer for Substrate Release
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Caged compounds are molecules that release a protective substrate to free a biologically active substrate upon treatment with light of sufficient energy and duration. A notable limitation of this approach is difficulty in determining the degree of photoactivation in tissues or opaque solutions because light reaching the desired location is obstructed. Here, we have addressed this issue by developing an in situ electrochemical method in which the amount of caged molecule photorelease is determined by fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes. Using p-hydroxyphenyl glutamate (pHP-Glu) as our model system, we generated a linear calibration curve for oxidation of 4-hydroxyphenylacetic acid (4HPAA), the group from which the glutamate molecule leaves, up to a concentration of 1000 μM. Moreover, we are able to correct for the presence of residual pHP-Glu in solution as well as the light artifact that is produced. A corrected calibration curve was constructed by photoactivation of pHP-Glu in a 3 μL photoreaction vessel and subsequent analysis by high-performance liquid chromatography. This approach has yielded a linear relationship between 4HPAA concentration and oxidation current, allowing the determination of released glutamate independent of the amount of light reaching the chromophore. Moreover, we have successfully validated the newly developed method by in situ measurement in a whole, intact zebrafish brain. This work demonstrates for the first time the in situ electrochemical monitoring of caged compound photochemistry in brain tissue with FSCV, thus facilitating analyses of neuronal function.
- Jarosova, Romana,Kaplan, Sam V.,Field, Thomas M.,Givens, Richard S.,Senadheera, Sanjeewa N.,Johnson, Michael A.
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- The photo-favorskii reaction of p-hydroxyphenacyl compounds is initiated by water-assisted, adiabatic extrusion of a triplet biradical
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The p-hydroxyphenacyl group 1 is an effective photoremovable protecting group, because it undergoes an unusual photo-Favorskii rearrangement concomitant with the fast release (33, with a lifetime of about 0.6 ns. The release of diethyl phosphate determines the lifetime of the triplet state T1(1a), τ(T1) = 60 ps in wholly aqueous solution. Formation of a new photoproduct, p-hydroxybenzyl alcohol (6), was observed at moderate water concentrations in acetonitrile. It is formed by CO elimination from the elusive spirodione intermediate (4), followed by hydration of the resulting p-quinone methide (5). Computational studies show that CO elimination from the spirodione is a very facile process. Copyright
- Givens, Richard S.,Heger, Dominik,Hellrung, Bruno,Kamdzhilov, Yavor,Mac, Marek,Conrad II, Peter G.,Cope, Elizabeth,Lee, Jong I.,Mata-Segreda, Julio F.,Schowen, Richard L.,Wirz, Jakob
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- PRODUCTION OF HYDROXYPHENYLETHANOL GLYCOSIDES IN SUSPENSION CULTURES OF SYRINGA VULGARIS
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Cell suspension cultures of Syringa vulgaris accumulate up to 16 percent of their dry wt as a mixture of hydroxyphenylethanol glycosides.The main component is the caffeoyl ester, verbascoside (acteoside).Tyrosine and tyramine are efficient biosynthetic precursors of the 4-hydroxy- and 3,4-dihydroxyphenylethanol moieties of these glycosides.Key Word Index- Syringa vulgaris; Oleaceae; lilac; cell cultures; biosynthesis; hydroxyphenylethanol glycosides; salidroside; verbascoside; caffeic acid.
- Ellis, B. E.
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- Supramolecular Storage and Controlled Photorelease of an Oxidizing Agent using a Bambusuril Macrocycle
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The oxidizing ability of peroxodisulfate upon complexation inside the Bambusuril macrocycle cavity is inhibited. This dianionic agent can be released on demand from its stable 1:1 complex in water (log Ka=6.9 m?1) by addition of a more strongly bound anion, such as iodide (log Ka=7.1 m?1), which can also be delivered in situ upon irradiation from a 4-hydroxyphenacyl iodide derivative with spatial and temporal precision. The oxidizing properties of peroxodisulfate ions liberated from the complex recover and can take part in subsequent chemical transformations.
- Torti, Edoardo,Havel, Václav,Yawer, Mirza A.,Ludvíková, Lucie,Babiak, Michal,Klán, Petr,Sindelar, Vladimir
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- A 'photorelease, catch and photorelease' strategy for bioconjugation utilizing a p-hydroxyphenacyl group
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A bioorthogonal 'catch and photorelease' strategy, which combines alkyne-azide cycloaddition between p-hydroxyphenacyl azide and alkyne derivatives to form a 1,2,3-triazole adduct and subsequent photochemical release of the triazole moiety via a photo-Favorskii rearrangement, is introduced. The first step can also involve photorelease of a strained alkyne and its Cu-free click reaction with azide.
- Madea,Slanina,Klán
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- Facile 1,2-aryl migration of 2-halomethyl-2-(4'-hydroxyphenyl) ketals: A novel single step synthesis of 4-hydroxyphenylacetic acid and its derivatives
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1,2-Aryl migration of 1-halomethyl-2-(4-hydroxyphenyl) ketals, obtained from 2-bromomethyl 4-hydroxyacetophenone, under mild basic conditions have been shown to give 4-hydroxyphenylacetic acid or its derivatives which are key intermediates in the preparation of Atenolol, a well known cardiac β-blocker.
- Kumar, Ashok,Rane, Ramkrishna A.,Ravindran, Vaikyparambil K.,Dike, Suneel Y.
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- SESQUITERTENE LACTONES FROM LACTUCA LACINIATA
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From the roots of Lactuca laciniata, six new sesquiterpene lactones, 9α-hydroxyzaluzanin C, 9α-hydroxy-11,13α-dihydrozaluzanin C, lactucopicriside, lactuside A and lactuside B, have been isolated together with known compounds, macrocliniside A, glucozaluzanin C, 11,13-α-dihydroglucozaluzanin C, 11,β,13-dihydrolactucin and dihydrosyntamarin.The structures were establishes by spectral data and X-ray diffraction analysis.Key Word Index - Lactuca laciniata; Compositae; sesquiterpene lactones; 9α-hydroxyzaluzanin C; 9α-hydroxy-11,13α-dihydrozaluzanin C; lactucopicriside; lactulide A; lactuside A; lactuside B.
- Nishimura, Keiichi,Miyase, Toshio,Ueno, Akira,Noro, Tadataka,Muroyanagi, Masanori,Fukushima, Seigo
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- Sesquiterpene lactones from Ixeris tamagawaensis KITAM. III
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Two new germacranolides, ixerins H and I, and three new melampolides, ixerins J, K and L were isolated from the polar and less polar fractions of Ixeris tamagawaensis KITAM., respectively. The structures and stereochemistry were established partly by chemical transformations and mainly by the use of 1H- and 13C-nuclear magnetic resonance spectroscopy.
- Asada,Miyase,Fukushima
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- Formation of Coelenteramine from 2-Peroxycoelenterazine in the Ca2+-Binding Photoprotein Aequorin
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Aequorin consists of apoprotein (apoAequorin) and (S)-2-peroxycoelenterazine (CTZ-OOH) and is considered to be a transient-state complex of an enzyme (apoAequorin) and a substrate (coelenterazine and molecular oxygen) in the enzymatic reaction. The degradation process of CTZ-OOH in aequorin was characterized under various conditions of protein denaturation. By acid treatment, the major product from CTZ-OOH was coelenteramine (CTM), but not coelenteramide (CTMD), and no significant luminescence was observed. The counterparts of CTM from CTZ-OOH were identified as 4-hydroxyphenylpyruvic acid (4HPPA) and 4-hydroxyphenylacetic acid (4HPAA) by liquid chromatography/electrospray ionization–time-of-flight mass spectrometry (LC/ESI-TOF-MS). In the luminescence reaction of aequorin with Ca2+, similar amounts of 4HPPA and 4HPAA were detected, indicating that CTM is formed by two pathways from CTZ-OOH through dioxetanone anion and not by hydrolysis from CTMD.
- Hosoya, Takamitsu,Inouye, Satoshi,Nakamura, Mitsuhiro
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- Rapid biosynthesis of phenolic glycosides and their derivatives from biomass-derived hydroxycinnamates
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Biomass-derived hydroxycinnamates (mainly includingp-coumaric acid and ferulic acid), which are natural sources of aromatic compounds, are highly underutilized resources. There is a need to upgrade them to make them economically feasible. Value-added phenolic glycosides and their derivatives, both belonging to a class of plant aromatic natural products, are widely used in the nutraceutical, pharmaceutical, and cosmetic industries. However, their complex aromatic structures make their efficient biosynthesis a challenging process. To overcome this issue, we created three novel synthetic cascades for the biosynthesis of phenolic glycosides (gastrodin, arbutin, and salidroside) and their derivatives (hydroquinone, tyrosol, hydroxytyrosol, and homovanillyl alcohol) fromp-coumaric acid and ferulic acid. Moreover, because the biomass-derived hydroxycinnamates directly provided aromatic units, the cascades enabled efficient biosynthesis. We achieved substantially high production rates (up to or above 100-fold enhancement) relative to the glucose-based biosynthesis. Given the ubiquity of the aromatic structure in natural products, the use of biomass-derived aromatics should facilitate the rapid biosynthesis of numerous aromatic natural products.
- Zhao, Mingtao,Hong, Xulin,Abdullah,Yao, Ruilian,Xiao, Yi
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p. 838 - 847
(2021/02/09)
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- Efficient Synthesis of Phenylacetate and 2-Phenylethanol by Modular Cascade Biocatalysis
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The green and sustainable synthesis of chemicals from renewable feedstocks by a biotransformation approach has gained increasing attention in recent years. In this work, we developed enzymatic cascades to efficiently convert l-phenylalanine into 2-phenylethanol (2-PE) and phenylacetic acid (PAA), l-tyrosine into tyrosol (p-hydroxyphenylethanol, p-HPE) and p-hydroxyphenylacetic acid (p-HPAA). The enzymatic cascade was cast into an aromatic aldehyde formation module, followed by an aldehyde reduction module, or aldehyde oxidation module, to achieve one-pot biotransformation by using recombinant Escherichia coli. Biotransformation of 50 mM l-Phe produced 6.76 g/L PAA with more than 99 % conversion and 5.95 g/L of 2-PE with 97 % conversion. The bioconversion efficiencies of p-HPAA and p-HPE from l-Tyr reached to 88 and 94 %, respectively. In addition, m-fluoro-phenylalanine was further employed as an unnatural aromatic amino acid substrate to obtain m-fluoro-phenylacetic acid; '96 % conversion was achieved. Our results thus demonstrated high-yielding and potential industrial synthesis of above aromatic compounds by one-pot cascade biocatalysis.
- Mao, Zuoxi,Liu, Lijun,Zhang, Yang,Yuan, Jifeng
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p. 2676 - 2679
(2020/06/03)
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- Reducing Agent-Mediated Nonenzymatic Conversion of 2-Oxoglutarate to Succinate: Implications for Oxygenase Assays
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l-Ascorbate (l-Asc) is often added to assays with isolated FeII- and 2-oxoglutarate (2OG)-dependent oxygenases to enhance activity. l-Asc is proposed to be important in catalysis by some 2OG oxygenases in vivo. We report observations on the nonenzymatic conversion of 2OG to succinate, which is mediated by hydrogen peroxide generated by the reaction of l-Asc and dioxygen. Slow nonenzymatic oxidation of 2OG to succinate occurs with some, but not all, other reducing agents commonly used in 2OG oxygenase assays. We intend these observations will help in the robust assignment of substrates and inhibitors for 2OG oxygenases.
- Khan, Amjad,Schofield, Christopher J.,Claridge, Timothy D. W.
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p. 2898 - 2902
(2020/08/21)
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- Copper and L-(?)-quebrachitol catalyzed hydroxylation and amination of aryl halides under air
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L-(?)-Quebrachitol, a natural product obtained from waste water of the rubber industry, was utilized as an efficient ligand for the copper-catalyzed hydroxylation and amination of aryl halides to selectively give phenols and aryl amines in water or 95percent ethanol. In addition, the hydroxylation of 2-chloro-4-hydroxybenzoic acid was validated on a 100-g scale under air.
- Bao, Xuefei,Chen, Guoliang,Dong, Jinhua,Du, Fangyu,Li, Hui,Liang, Xinjie,Wu, Ying,Zhang, Yongsheng
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supporting information
(2020/08/03)
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- Synthesis and biological evaluation of 3-arylcoumarin derivatives as potential anti-diabetic agents
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A variety of substituted 3-arylcoumarin derivatives were synthesised through microwave radiation heating. The method has characteristics of environmental friendliness, economy, simple separation, and purification process, less by-products and high reaction yield. Those 3-arylcoumarin derivatives were screened for antioxidant, α-glucosidase inhibitory and advanced glycation end-products (AGEs) formation inhibitory. Most compounds exhibited significant antioxidant and AGEs formation inhibitory activities. Anti-diabetic activity studies showed that compounds 11 and 17 were equipotent to the standard drug glibenclamide in vivo. According to the experimental results, the target compound 35 can be used as a lead compound for the development of new anti-diabetic drugs. The whole experiment showed that anti-diabetic activity is prevalent in 3-arylcoumarins, which added a new natural skeleton to the development of anti-diabetic active drugs.
- Hu, Yuheng,Wang, Bing,Yang, Jie,Liu, Teng,Sun, Jie,Wang, Xiaojing
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- Synthesis and biological evaluation of 3-arylcoumarins as potential anti-Alzheimer's disease agents
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Alzheimer's disease, a neurodegenerative illness, has the extremely complex pathogenesis. Accumulating evidence indicates there is a close relationship between several enzymes and Alzheimer's disease. Various substituted 3-arylcoumarin derivatives were synthesised, and their in vitro activity, including cholinesterase inhibitory activity, monoamine oxidase inhibitory activity, and antioxidant activity were investigated. Most of the compounds exhibited high activity; therefore 3-arylcoumarin compounds have the potential as drug candidates for the treatment of Alzheimer's disease.
- Yang, Jie,Zhang, Pingping,Hu, Yuheng,Liu, Teng,Sun, Jie,Wang, Xiaojing
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p. 651 - 656
(2019/02/19)
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- Total Synthesis of Enisorine D and its Analogues
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The first total synthesis of enisorine D, a natural product isolated from the marine sponge Iotrochota cf. iota, is described in 64percent overall yield. The target molecule, which is an inhibitor of T3SS-dependent Yope secretion of Y. pseudotuberculosis, is achieved in seven linear steps from tyramine via simple and effective transformations that include bromination, acylation, alkylation, azidation, reduction and routine acid-amine coupling. A total of sixteen analogues are prepared by coupling with eight different cinnamic acids, two bromopyrrole carboxylic acids, five phenyl carboxylic acids and picolinic acid.
- Hussain, Mulla Althafh,Khan, Faiz Ahmed,Shashi, Shashi
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p. 4601 - 4610
(2019/12/11)
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- Application of quebrachitol in hydrolysis reaction of copper-catalyzed aryl halide
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The invention belongs to the technical field of drug synthesis, and provides application of quebrachitol in a hydrolysis reaction of a copper-catalyzed aryl halide. According to the hydrolysis reaction, copper serves as a catalyst, quebrachitol serves as a ligand, and the hydrolysis reaction is carried out on the aryl halide. The invention further provides a catalytic system of the hydrolysis reaction of the aryl halide. The reaction system comprises the copper catalyst, the quebrachitol, alkali and water, and the system is environmentally friendly and is suitable for industrial application.
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Paragraph 0051-0053
(2019/07/16)
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- Selective oxidation of aliphatic C-H bonds in alkylphenols by a chemomimetic biocatalytic system
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Selective oxidation of aliphatic C-H bonds in alkylphenols serves significant roles not only in generation of functionalized intermediates that can be used to synthesize diverse downstream chemical products, but also in biological degradation of these environmentally hazardous compounds. Chemo-, regio-, and stereoselectivity; controllability; and environmental impact represent the major challenges for chemical oxidation of alkylphenols. Here, we report the development of a unique chemomimetic biocatalytic system originated from the Gram-positive bacterium Corynebacterium glutamicum. The system consisting of CreHI (for installation of a phosphate directing/ anchoring group), CreJEF/CreG/CreC (for oxidation of alkylphenols), and CreD (for directing/anchoring group offloading) is able to selectively oxidize the aliphatic C-H bonds of p-And m-Alkylated phenols in a controllable manner. Moreover, the crystal structures of the central P450 biocatalyst CreJ in complex with two representative substrates provide significant structural insights into its substrate flexibility and reaction selectivity.
- Du, Lei,Dong, Sheng,Zhang, Xingwang,Jiang, Chengying,Chen, Jingfei,Yao, Lishan,Wang, Xiao,Wan, Xiaobo,Liu, Xi,Wangi, Xinquan,Huang, Shaohua,Cui, Qiu,Feng, Yingang,Liu, Shuang-Jiang,Li, Shengying
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p. E5129 - E5137
(2017/07/04)
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- Production method of p-hydroxyphenylacetamide
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The invention relates to a production method of p-hydroxyphenylacetamide and belongs to the medicine field. Phenol and glyoxylic acid are taken as raw materials to be prepared into a competitive product via processes of synthesis, reduction and ammonolysis. The production method has the advantages that the optimal synthesis process is determined, yield of the obtained p-hydroxyphenylacetamide can reach over 80%, purity can reach more than 99%, and the technical process is simpler, easy to implement and environment friendly.
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Paragraph 0071-0083
(2017/10/07)
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- A method for the preparation of phenylacetic acid derivatives
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The invention discloses a preparation method of a substituted phenylacetic acid derivative. The method comprises the following steps: 1, carrying out a sulfonylation reaction on substituted phenylglycine and sulfuryl chloride under the action of an alkali, and post-processing after completing the reaction to obtain an intermediate; and 2, carrying out a deamination reaction on the intermediate obtained in step 1 under the action of an organic acid and a reducing agent, and post-processing after completing the reaction to obtain the substituted phenylacetic acid derivative. The raw material phenylglycine used in the above route can be very easily purchased from the market, and is cheap and easily available. The preparation method has the advantages of short process route, mild reaction conditions, simple operation, high reaction yield and low total lost.
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Paragraph 0051; 0052; 0053; 0054
(2017/05/30)
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- Novel mild synthesis of high-added-value p -hydroxyphenyl acetic acid and 3,4-dihydroxyphenyl acetic acid using the acidic clay/hydrogen peroxide catalytic system
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Acid-activated clays KSF and KSF/0 were successfully used in the hydrogen peroxide conversion of phenyl acetic acid to high-added phenolic compounds: p-hydroxyphenyl acetic acid and 3,4-dihydroxyphenyl acetic acid, endowed with a powerful antioxidant capacity. The catalytic conversion enhancement could be correlated to the total surface acidity and the high iron content of the catalysts KSF/0 and KSF, respectively. The synthetic route described here was conducted under mild conditions with very low degree of mineralization and without significant Fe ion leaching observations. The synthesis reaction is operationally simple and could find application for industrial purposes.
- Bouguerra Neji, Soumaya,Azabou, Samia,Contreras, Sandra,Medina, Francisco,Bouaziz, Mohamed
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p. 285 - 291
(2016/04/19)
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- 4-Hydroxyphenacyl Ammonium Salts: A Photoremovable Protecting Group for Amines in Aqueous Solutions
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Irradiation of N-protected p-hydroxyphenacyl (pHP) ammonium caged derivatives at 313 nm releases primary and secondary amines or ammonia in nearly quantitative yields via the photo-Favorskii reaction when conducted in acidic or neutral aqueous buffered media. The reaction efficiencies are strongly dependent on the pH with the most efficient and highest yields obtained when the pH of the media maintains the ammonium and p-hydroxyl groups as their conjugate acids. For example, the overall quantum yields of simple secondary amines release are 0.5 at acidic pH from 3.9 to 6.6 dropping to 0.1 at neutral pH 7.0 and 0.01 at pH 8.4. Speciation studies provide an acid-base profile that helps define the scope and limitations of the reaction. When the pKa of the ammonium group is lower than that of the phenolic hydroxyl group, as is the case for the α-amino-protected amino acids, the more acidic ammonium ion deprotonates as the media pH is changed from acidic toward neutral or basic, thus diminishing the leaving group ability of the amino group. This, in turn, lowers the propensity for the photo-Favorskii rearrangement reaction to occur and opens the reaction pathway to alternative competing photoreduction process.
- Bownik, Iwona,?ebej, Peter,Literák, Jaromír,Heger, Dominik,?imek, Zdeněk,Givens, Richard S.,Klán, Petr
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p. 9713 - 9721
(2015/10/12)
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- In the cleaving org. compd. ether bond
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PROBLEM TO BE SOLVED: To provide a cleavage method of a methyl ether bond in an organic compound for cleaving the methyl ether bond in the organic compound which is usable as various synthesis methods for organic compounds without especially using a solvent or a post-treatment agent. SOLUTION: The method is characterized in that an organic compound having a methyl ether bond is contacted with hydrogen iodide gas at room temperature without dissolving a solvent so that the methyl ether bond is cleaved. COPYRIGHT: (C)2013,JPOandINPIT
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Paragraph 0075-0078
(2016/12/22)
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- Caged Fluoride: Photochemistry and Applications of 4-Hydroxyphenacyl Fluoride
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The quantitative, efficient (Φ = 0.8) photorelease of the fluoride ion upon UV-irradiation in aqueous media is introduced. The 4-hydroxyphenacyl chromophore is simultaneously transformed into UV-transparent 4-hydroxyphenylacetate via a photo-Favorskii rearrangement. The application of this process is demonstrated by photoinduced etching of mica and silicon by AFM.
- Slanina, Tomá?,?ebej, Peter,Heckel, Alexander,Givens, Richard S.,Klán, Petr
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supporting information
p. 4814 - 4817
(2015/10/12)
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- Photorelease of incarcerated guests in aqueous solution with phenacyl esters as the trigger
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We report the clean, efficient photorelease of a series of carboxylic acids embedded in octa acid (OA) host and protected by a p-hydroxyphenacyl cage. A key role is played by the cage by providing hydrophobicity for entry into the OA enclosure and yet readily removable as a photoactivated protecting group for release from the host. The rapid photo-Favorskii rearrangement of the departing chromophore does not react with the host OA but diminishes hydrophobicity of the OA contents, leading to their facile release into the solvent.
- Jagadesan, Pradeepkumar,Da Silva, José P.,Givens, Richard S.,Ramamurthy
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p. 1276 - 1279
(2015/05/20)
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- Oxidative cleavage of α-sulfonyl ketones to carboxylic acids with Ce(NH4)2(NO3)6
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Tandem oxidative cleavage of α-sulfonyl arylketones 2 with the combination of Ce(NH4)2(NO3)6 and O2 in MeCN afforded carboxylic acids 3 in moderate to good yields. The plausible reaction mechanism has
- Chang, Meng-Yang,Tsai, Chung-Yu
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supporting information
p. 5548 - 5550
(2014/12/11)
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- 2-Diazo-1-(4-hydroxyphenyl)ethanone: A versatile photochemical and synthetic reagent
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α-Diazo arylketones are well-known substrates for Wolff rearrangement to phenylacetic acids through a ketene intermediate by either thermal or photochemical activation. Likewise, α-substituted p-hydroxyphenacyl (pHP) esters are substrates for photo-Favorskii rearrangements to phenylacetic acids by a different pathway that purportedly involves a cyclopropanone intermediate. In this paper, we show that the photolysis of a series of α-diazo-p- hydroxyacetophenones and p-hydroxyphenacyl (pHP) α-esters both generate the identical rearranged phenylacetates as major products. Since α-diazo-p-hydroxyacetophenone (1a, pHP N2) contains all the necessary functionalities for either Wolff or Favorskii rearrangement, we were prompted to probe this intriguing mechanistic dichotomy under conditions favorable to the photo-Favorskii rearrangement, i.e., photolysis in hydroxylic media. An investigation of the mechanism for conversion of 1a to p-hydroxyphenyl acetic acid (4a) using time-resolved infrared (TRIR) spectroscopy clearly demonstrates the formation of a ketene intermediate that is subsequently trapped by solvent or nucleophiles. The photoreaction of 1a is quenched by oxygen and sensitized by triplet sensitizers and the quantum yields for 1a-c range from 0.19 to a robust 0.25. The lifetime of the triplet, determined by Stern-Volmer quenching, is 31 ns with a rate for appearance of 4a of k = 7.1 × 10 6 s-1 in aq. acetonitrile (1:1 v:v). These studies establish that the primary rearrangement pathway for 1a involves ketene formation in accordance with the photo-Wolff rearrangement. Furthermore we have also demonstrated the synthetic utility of 1a as an esterification and etherification reagent with a variety of substituted α-diazo-p- hydroxyacetophenones, using them as synthons for efficiently coupling it to acids and phenols to produce pHP protect substrates. The Royal Society of Chemistry and Owner Societies.
- Senadheera, Sanjeewa N.,Evans, Anthony S.,Toscano, John P.,Givens, Richard S.
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p. 324 - 341
(2014/02/14)
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- Intermediate partitioning kinetic isotope effects for the NIH shift of 4-hydroxyphenylpyruvate dioxygenase and the hydroxylation reaction of hydroxymandelate synthase reveal mechanistic complexity
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4-Hydroxyphenylpyruvate dioxygenase (HPPD) and hydroxymandelate synthase (HMS) are similar enzymes that catalyze complex dioxygenation reactions using the substrates 4-hydroxyphenylpyruvate (HPP) and dioxygen. Both enzymes decarboxylate HPP and then hydroxylate the resulting hydroxyphenylacetate (HPA). The hydroxylation reaction catalyzed by HPPD displaces the aceto substituent of HPA in a 1,2-shift to form 2,5-dihydroxyphenylacetate (homogentisate, HG), whereas the hydroxylation reaction of HMS places a hydroxyl on the benzylic carbon forming 3′-hydroxyphenylacetate (S-hydroxymandelate, HMA) without ensuing chemistry. The wild-type form of HPPD and variants of both enzymes uncouple to form both native and non-native products. We have used intermediate partitioning to probe bifurcating steps that form these products by substituting deuteriums for protiums at the benzylic position of the HPP substrate. These substitutions result in altered ratios of products that can be used to calculate kinetic isotope effects (KIE) for the formation of a specific product. For HPPD, secondary normal KIEs indicate that cleavage of the bond in the displacement reaction prior to the shift occurs by a homolytic mechanism. NMR analysis of HG derived from HPPD reacting with enantiomerically pure R-3′-deutero-HPP indicates that no rotation about the bond to the radical occurs, suggesting that collapse of the biradical intermediate is rapid. The production of HMA was observed in HMS and HPPD variant reactions. HMS hydroxylates to form exclusively S-hydroxymandelate. When HMS is reacted with R-3′-deutero-HPP, the observed kinetic isotope effect represents geometry changes in the initial transition state for the nonabstracted proton. These data show evidence of sp3 hybridization in a HPPD variant and sp 2 hybridization in HMS variants, suggesting that HMS stabilizes a more advanced transition state in order to catalyze H-atom abstraction.
- Shah, Dhara D.,Conrad, John A.,Moran, Graham R.
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p. 6097 - 6107
(2013/09/23)
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- Highly efficient and selective deprotection method for prenyl, geranyl, and phytyl ethers and esters using borontrifluoride-etherate
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An efficient, simple, and practical method has been developed for the deprotection of prenyl, geranyl, and phytyl ethers and esters of aromatic and aliphatic compounds using borontrifluoride-etherate (BF3· OEt2) at room temperature in good to excellent yields for the first time. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file. Copyright Taylor & Francis Group, LLC.
- Narender,Venkateswarlu,Madhur,Reddy, K. Papi
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- Chemoselective hydrogenation catalyzed by Pd on spherical carbon
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We have developed a highly chemoselective hydrogenation method using a novel palladium catalyst supported on spherical carbon (0.5 % Pd/SC). The 0.5 % Pd/SC exhibited a novel catalytic activity and could achieve the chemoselective hydrogenation of alkynes, alkenes, azides, nitro groups, and aliphatic O-tert-butyldimethylsilyl (TBS) ethers without hydrogenolysis of benzyl esters, benzyl ethers, nitriles, aromatic ketones, N-carbobenzyloxy (N-Cbz) protective groups, and aromatic O-TBS ethers. Highly selective spheres: The chemoselective hydrogenation of C-C multiple bonds, azides, nitro groups, and aliphatic O-tert-butyldimethylsilyl (TBS) ethers is achieved in the presence of benzyl esters, benzyl ethers, nitriles, aromatic ketones, N-carbobenzyloxy (Cbz) protective groups, and aromatic O-TBS ethers by a novel heterogeneous palladium catalyst supported on spherical carbon (0.5 % Pd/SC). Copyright
- Esaki, Hiroyoshi,Hattori, Tomohiro,Tsubone, Aya,Mibayashi, Satoko,Sakata, Takao,Sawama, Yoshinari,Monguchi, Yasunari,Yasuda, Hidehiro,Nosaka, Kazuto,Sajiki, Hironao
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p. 3629 - 3635
(2014/01/06)
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- Alcaligenes faecalis penicillin G acylase-catalyzed enantioselective acylation of dl-phenylalanine and derivatives in aqueous medium
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A new strategy based on enantioselective acylation properties of relatively unknown penicillin G acylase from Alcaligenes faecalis has been developed for the production of pharmacologically interesting enantiomerically pure d-phenylalanine. In order to get high reaction rate and enantioselectivity, two key factors (pH and temperature) and eight different acyl donors were optimized, and the optimal acylation reaction was carried out at pH 10, 35 °C, using phenylacetamide as the acyl donor. This enantioselective acylating method is also illustrated by the effective production of five different p-substituted phenylalanine derivatives in enantiopure.
- Gong, Xiangyu,Su, Erzheng,Wang, Pixiang,Wei, Dongzhi
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supporting information; experimental part
p. 5398 - 5402
(2011/10/19)
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- P-Hydroxyphenacyl photoremovable protecting groups Robust photochemistry despite substituent diversity
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A broadly based investigation of the effects of a diverse array of substituents on the photochemical rearrangement of p-hydroxyphenacyl esters has demonstrated that common substituents such as F, MeO, CN, CO2R, CONH2, and CH3 have little effect on the rate and quantum efficiencies for the photo-Favorskii rearrangement and the release of the acid leaving group or on the lifetimes of the reactive triplet state. A decrease in the quantum yields across all substituents was observed for the release and rearrangement when the photolyses were carried out in buffered aqueous media at pHs that exceeded the ground-state pKa of the chromophore where the conjugate base is the predominant form. Otherwise, substituents have only a very modest effect on the photoreaction of these robust chromophores.
- Givens, Richard S.,Stensrud, Kenneth,Conrad, Peter G.,Yousef, Abraham L.,Perera, Chamani,Senadheera, Sanjeewa N.,Heger, Dominik,Wirz, Jakob
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scheme or table
p. 364 - 384
(2011/06/22)
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- Iodide-catalyzed reductions: Development of a synthesis of phenylacetic acids
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A new convenient and scalable synthesis of phenylacetic acids has been developed via the iodide catalyzed reduction of mandelic acids. The procedure relies on in situ generation of hydroiodic acid from catalytic sodium iodide, employing phosphorus acid as the stoichiometric reductant.
- Milne, Jacqueline E.,Storz, Thomas,Colyer, John T.,Thiel, Oliver R.,Dilmeghani Seran, Mina,Larsen, Robert D.,Murry, Jerry A.
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experimental part
p. 9519 - 9524
(2012/01/06)
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- Deposition of new thia-containing Schiff-base iron (III) complexes onto carbon nanotube-modified glassy carbon electrodes as a biosensor for electrooxidation and determination of amino acids
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Multiwall carbon nanotubes (MWCNTs) were used as an immobilization matrix to incorporate an Fe (III)-Schiff base complex as an electron-transfer mediator onto a glassy carbon electrode surface. First, the preheated glassy carbon was subjected to abrasive immobilization of MWCNTs by gently rubbing the electrode surface on filter paper supporting the carbon nanotubes. Second, the electrode surface was modified by casting 100 μL of an Fe (III)-complex solution (0.01 M in ACN). The cyclic voltammograms of the modified electrode in an aqueous solution displayed a pair of well-defined, stable and nearly reversible reductive oxidation redox systems with surface confined characteristics. Combinations of unique electronic and electrocatalytic properties of MWCNTs and Fe (III)-Schiff base complexes resulted in a remarkable synergistic augmentation of the response. The electrochemical behavior and stability of the modified electrode in aqueous solutions at pH 1-9 were characterized by cyclic voltammetry. The apparent electron transfer rate constant (Ks) and transfer coefficient (a) were determined by cyclic voltammetry and were approximately 7 s-1 and 0.55, respectively. The modified electrodes showed excellent catalytic activity towards the oxidation of amino acids at an unusually positive potential in acidic solution. They also displayed inherent stability at a wide pH range, fast response time, high sensitivity, low detection limit and had a remarkably positive potential oxidation of amino acids that decreased the effect of interferences in analysis. The linear concentration range, limits of detection (LOD), limits of quantization (LOQ) and relative standard deviation of the proposed sensor for the amino acid detection were 1-55,000, 1.10-13.70, 2.79-27.14 and 1.30-5.11, respectively.
- Saghatforoush, Lotfali,Hasanzadeh, Mohammad,Shadjou, Nasrin,Khalilzadeh, Balal
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experimental part
p. 1051 - 1061
(2011/04/16)
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- Novel benzimidazole derivatives as selective CB2 agonists
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The preparation and evaluation of a novel class of CB2 agonists based on a benzimidazole moiety are reported. They showed binding affinities up to 1 nM towards the CB2 receptor with partial to full agonist potencies. They also demonstrated good to excellent selectivity (>1000-fold) over the CB1 receptor.
- Pagé, Daniel,Balaux, Elise,Boisvert, Luc,Liu, Ziping,Milburn, Claire,Tremblay, Maxime,Wei, Zhongyong,Woo, Simon,Luo, Xuehong,Cheng, Yun-Xing,Yang, Hua,Srivastava, Sanjay,Zhou, Fei,Brown, William,Tomaszewski, Miroslaw,Walpole, Christopher,Hodzic, Leila,St-Onge, Stéphane,Godbout, Claude,Salois, Dominic,Payza, Keymal
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scheme or table
p. 3695 - 3700
(2009/04/04)
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- Ultrafast time-resolved transient absorption and resonance Raman spectroscopy study of the photodeprotection and rearrangement reactions of p-hydroxyphenacyl caged phosphates
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The kinetics and mechanism of the photodeprotection and rearrangement reactions for the pHP phototrigger compounds p-hydroxyphenacyl diethyl phosphate (HPDP) and diphenyl phosphate (HPPP) were studied using transient absorption (TA) and picosecond time-resolved resonance Raman (ps-TR3) spectroscopy. TA spectroscopy was employed to detect the dynamics of the triplet precursor decay as well as to investigate the influence of the solvent and leaving group on the triplet quenching process. Ps-TR3 spectroscopy was used to directly monitor the formation dynamics for the photosolvolytic rearrangement product and its solvent and leaving group dependence. The TA and TR3 spectroscopy experiments were also used to characterize the structural and electronic properties of the triplet precursor to the HPDP and HPPP deprotection reactions. The solvent effect observed in conjunction with the leaving group dependence of the triplet decay dynamics are consistent with a concerted solvent assisted triplet cleavage through a heterolytic mechanism for the HPDP and HPPP photodeprotection process. Correlation of the dynamics between the deprotection and rearrangement processes reveals there is a consecutive mechanism and the involvement of an intermediate between the two reaction steps. The reaction rate of the deprotection and rearrangement steps and the influence of the solvent and leaving group were determined and evaluated based on kinetic modeling of the dynamical data obtained experimentally for HPDP and HPPP in H2O/MeCN mixed solvents with varying water concentration in the solvent system. A solvation complex with a contact ion pair character was proposed to be the intermediate involved in the deprotection and rearrangement pathway. The results here combined with our previous study on the photophysical events occurring on the early picosecond time scale (Ma; et al. J. Am. Chem. Soc. 2005, 127, 1463-1472) provide a real time overall mechanistic description for the photodeprotection and rearrangement reactions of pHP caged phosphate phototrigger compounds.
- Ma, Chensheng,Kwok, Wai Ming,Chan, Wing Sum,Du, Yong,Kan, Jovi Tze Wai,Toy, Patrick H.,Phillips, David Lee
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p. 2558 - 2570
(2007/10/03)
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- Highly chemoselective hydrogenation method using novel finely dispersed palladium catalyst on silk-fibroin: Its preparation and activity
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A palladium-fibroin complex (Pd/Fib) was prepared by soaking silk-fibroin in MeOH solution of Pd(OAc)2 for 2 days (under Ar atmosphere) - 4 days (under air). Pd(OAc)2 was gradually absorbed by fibroin and the rapid reduction of fibroin conjugated Pd(OAc)2 proceeded with MeOH as a reductant at room temperature to be the Pd(0) complex. Pd/Fib catalyzed chemoselective hydrogenation of acetylenes, olefins and azides in the presence of aromatic ketones and aldehydes, halides, N-Cbz protective groups and benzyl esters which are readily hydrogenated using Pd/C or Pd/C(en) as a catalyst.
- Ikawa, Takashi,Sajiki, Hironao,Hirota, Kosaku
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p. 2217 - 2231
(2007/10/03)
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- An efficient asymmetric synthesis of (S)-atenolol: Using hydrolytic kinetic resolution
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Enantiomerically pure (S)-atenolol was prepared by using (R,R) salen Co(III) complex for the resolution of terminal epoxide. This process was carried out at room temperature in excellent enantio selectivity. The method can be applied for large-scale preparation of (S)-atenolol without any problem.
- Subhas Bose,Venkat Narsaiah
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p. 627 - 630
(2007/10/03)
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- One step hair coloring compositions using salts
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A hair coloring composition comprising the following two compositions which are mixed just prior to application to the hair: (a) a composition comprising a water-soluble peroxygen oxidizing agent; and (b) a composition comprising one or more oxidative hair coloring agents selected from the group consisting of an aromatic diamine, an amino phenol, a naphthol, a polyhydric phenol, a catechol and mixtures thereof; wherein the composition comprising one or more oxidative hair coloring agents further comprises al least one water soluble carbonate releasing salts; and optionally a water soluble ammonium salt, is described.
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- A facile synthesis of phenylacetic acids via Willgerodt-Kindler reaction under PTC condition
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Phenylacetic acids are efficiently synthesized from acetophenones via thiomorpholides under Phase Transfer Catalytic (PTC) condition. The reaction proceeds efficiently by using triethyl benzyl ammonium chloride (TEBA) as PTC and the reaction time decreased dramatically upto 1/5th (24-5) to afford pure products in good to excellent yield.
- Alam, Mujahid,Adapa, Srinivas R.
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- Transition metal complexes as dye forming catalysts in hair coloring compositions
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A hair coloring composition comprising a first composition which comprises: (a) a dye forming transition metal salt or complex; which is first applied to the hair; and a second composition which comprises the following two compositions which are mixed just prior to application to the hair: (a) a composition comprising a water-soluble peroxygen oxidizing agent; and (b) a composition comprising one or more oxidative hair coloring agents selected from the group consisting of an aromatic diamine, an aminophenol, a polyhydric phenol a catechol and mixtures thereof.
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- Towards the rehabilitation of the Mathews' 'dry' hydrolysis reaction using microwave technology
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The Mathews' reaction is a one-pot preparation of carboxylic acids from their corresponding nitriles or amides by a 'dry' hydrolysis with phthalic acid or anhydride in the absence of water and solvent. Excellent isolated yields and selectivity (up to 99%) were attained within short reaction times (typically, 30 minutes) when the reaction was performed under microwave heating.
- Chemat, Farid
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p. 5555 - 5557
(2007/10/03)
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- p-Hydroxyphenacyl bromide as photoremoveable thiol label: A potential phototrigger for thiol-containing biomolecules
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p-Hydroxyphenacyl bromide is described as a photoremovable thiol protecting group on three biomolecules containing a free thiol group. The protecting group is efficiently incorporated by chemical coupling to the biomolecule in an ethanol-buffer mixture. The photofragmentations (λ=312 nm) were analyzed by UV, HPLC and MS methods, yielding over 70% of the free biomolecules. The concomitant formation of p-hydroxyphenylacetic thioesters derived from the corresponding thiols, as a sulfur-containing side-product, should not hinder the use of this protecting group for the caging of thiol-containing biomolecules.
- Specht, Alexandre,Loudwig, Sandra,Peng, Ling,Goeldner, Maurice
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p. 8947 - 8950
(2007/10/03)
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- Antibody-catalyzed hydrolysis of oligomeric esters: A model for the degradation of polymeric materials
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A catalytic antibody has been discovered that degrades oligomeric ester substrates.
- Bruemmer,Hoffman,Chen,Janda
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- A mild and convenient 'dry' hydrolysis of amides to carboxylic acids
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A one-pot preparation of carboxylic acids is described that proceeds from their corresponding amides by a 'dry' hydrolysis with phthalic anhydride in the absence of water and solvent. The method affords carboxylic acids in good yields and is applicable to a variety of substrates. (C) 2000 Elsevier Science Ltd.
- Chemat, Farid
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p. 3855 - 3857
(2007/10/03)
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- Mechanism of photosolvolytic rearrangement of p-hydroxyphenacyl esters: Evidence for excited-state intramolecular proton transfer as the primary photochemical step
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The photosolvolytic rearrangement of a variety of p-hydroxyphenacyl esters and related compounds 7-16 has been studied in solutions with up to 50% aqueous content, using product studies, triplet quenchers, and nanosecond laser flash photolysis. The p-hydroxyphenacyl moiety has recently been proposed as a new and efficient photoactivated protecting group in aqueous solution. Practical applications have been demonstrated, but much less is known about the mechanism of photoreaction. Our data support a novel mechanism in which the primary photochemical step from the singlet excited state is formal intramolecular proton transfer from the phenolic proton to the carbonyl oxygen of the distal ketone, mediated by solvent water, to generate the corresponding p-quinone methide phototautomer. This reactive intermediate (most likely in its excited state) subsequently expels the carboxylic acid with concerted rearrangement to a spiroketone intermediate, which subsequently leads to the final observed product, p- hydroxyphenylacetic acid. An alternative mechanism is deprotonation of the phenolic proton, loss of the carboxylate, and rearrangement to the spiroketone, all in one concerted primary photochemical step from S1.
- Zhang, Kai,Corrie, John E. T.,Munasinghe, V. Ranjit N.,Wan, Peter
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p. 5625 - 5632
(2007/10/03)
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- Synthesis of 13C-labeled possible intermediates in the biosynthesis of phenylethanoid derivatives, cornoside and rengyosides
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In order to clarify the biosynthetic pathway of C6-C2 unit compounds containing salidroside, cornoside, and rengyosides A and B in oleaceous plants, 13C-labeled putative precursors, 4-hydroxyphenylethanol, salidroside and cornoside, were prepared.
- Kuwajima, Hiroshi,Takai, Yoshitaka,Takaishi, Kiyokazu,Inoue, Kenichiro
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p. 581 - 586
(2007/10/03)
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- Oxidative decarbonylation of β-arylpyruvic acids using sodium perborate
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Oxidation of β-aryl- and β-heteroarylpyruvic acids using sodium perborate tetrahydrate (SPB) in aqueous solution at ambient temperature gives the corresponding arylacetic acids in good yield (68-86%). The mild conditions are convenient for the preparation of thermally unstable acids. In particular the method has been applied to the preparation of an unstable 5- nitroimidazol-2-yl ethanoic acid which could not be obtained using other reagents apparently due to enolisation of the pyruvic acid precursor. Attempts to achieve decarbonylation using calcium hypochlorite or SPB in acidic solution lead to the 2 chloromethyl derivatives. The novel 5- nitroimidazol-2-yl ethanoic acid, which was required as a precursor of molecules of biological interest, has been fully characterised and converted to a known amide. Reaction of this acid with Vilsmeier's reagent gave an enamine derivative and not the expected vinamidinium salt. This novel mode of reaction is attributable to intramolecular hydrogen-bonding and favourable conjugation.
- Morrow, Nicholas,Ramsden, Christopher A.,Sargent, Bruce J.,Wallett, Christiaan D.
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p. 9603 - 9612
(2007/10/03)
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- Kinetics and Mechanism of the Alkaline Hydrolysis of Pentachlorophenyl ω-(p-Hydroxyphenyl)alkanoates
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A kinetic study of the alkaline hydrolysis of pentachlorophenyl esters of ω-(p-hydroxyphenyl)alkanoic acids 3 shows that the dissociative route involving a spirodienone intermediate is not a feasible alternative to the normal associative BAC2 pathway.
- Cevasco, Giorgio,Thea, Sergio
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p. 269 - 272
(2007/10/03)
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- Hydrolytic profile for ester- or amide-linkage by carboxylesterases pI 5.3 and 4.5 from human liver
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Carboxylesterases (EC 3.1.1.1) from human liver were purified using Q- Sepharose, Sephadex G-150, isoelectrofocusing and Con A-Sepharose. The calculated molecular mass of the pI 5.3 enzyme was 120 kDa and 61 kDa from the results of Sephadex G-150 gel filtration and SDS-polyacrylamide gel electrophoresis (PAGE), respectively, suggesting that this enzyme is a dimer. On the other hand, carboxylesterase pI 4.5, with a molecular-mass of 64 kDa, was a monomer. The activities of both enzymes were inhibited by typical serine enzyme inhibitors. Amino acid sequence analysis of the purified enzymes pI 5.3 and 4.5 showed high homology with rabbit carboxylesterase form 1 and 2, respectively. The results also suggested that carboxylesterase pI 5.3 is identical to the deduced amino acid sequence from cDNA for HUI, and that carboxylesterase pI 4.5 is identical to the deduced amino acid sequence from the cDNA registered as human carboxylesterase (hCE-2) in GenBank. We first purified carboxylesterase pI 4.5 and investigated its hydrolytic activity upon various drugs. The two enzymes differed in substrate specificity. Prodrugs of angiotensin-converting enzyme inhibitors, such as delapril and imidapril, were converted to active metabolites by carboxylesterase pI 5.3, but not by carboxylesterase pI 4.5. The hydrolysis velocity of temocapril by carboxylesterase pI 5.3 was 12-fold faster than by carboxylesterase pI 4.5. In contrast, aspirin oxybutynin and procaine were hydrolyzed by only carboxylesterase pI 4.5. We also found that an amide- linkage in drugs, except for that in aniracetam was not a good substrate for the two enzymes. Consequently, carboxylesterases pI 5.3 and 4.5 maybe involved in the metabolism of various drugs containing an ester-linkage.
- Takai, Satomi,Matsuda, Ayuka,Usami, Yoshiko,Adachi, Tetsuo,Sugiyama, Tadashi,Katagiri, Yoshihiro,Tatematsu, Masae,Hirano, Kazuyuki
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p. 869 - 873
(2007/10/03)
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