- Discovery of a Diazo-Forming Enzyme in Cremeomycin Biosynthesis
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The molecular architectures and potent bioactivities of diazo-containing natural products have attracted the interest of synthetic and biological chemists. Despite this attention, the biosynthetic enzymes involved in diazo group construction have not been identified. Here, we show that the ATP-dependent enzyme CreM installs the diazo group in cremeomycin via late-stage N-N bond formation using nitrite. This finding should inspire efforts to use diazo-forming enzymes in biocatalysis and synthetic biology as well as enable genome-based discovery of new diazo-containing metabolites.
- Waldman, Abraham J.,Balskus, Emily P.
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- SEMECARPETIN, A BIFLAVANONE FROM SEMECARPUS ANACARDFIUM
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Key Word Index - Semecarpus anacardium; Anacardiceae; biflavanones; 1H NMR and mass spectra; semecarpetin.Abstract - A new biflavanone, semecarpetin, has been recently isolated from the nut shells of Semecarpus anacardium.Its structure has been characterized on the basis of spectral and chemical data as 7''-hydroxy-7,3''',4',4'''-tetramethoxybi(8'',3')flavanone.
- Murthy, S. S. N.
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- Palladium-catalyzed ortho-C-H hydroxylation of benzoic acids
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A simple Pd(OAc)2 catalyzed ortho-hydroxylation of benzoic acids using TBHP as the sole oxidant has been explored. This protocol features relatively broad substrate scope and operational simplicity. The compatibility of ortho-substituted substrates is an effective complement to the previous ortho-hydroxylation reaction.
- Luo, Feihua,He, Shuhua,Gou, Quan,Chen, Jinyang,Zhang, mingzhong
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- Catalytic oxidation of alcohols and alkyl benzenes to carbonyls using Fe3O4?SiO2?(TEMPO)-: Co -(Chlorophyll-CoIII) as a bi-functional, self-co-oxidant nanocatalyst
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Chlorophyll b was extracted from heliotropium europaeum plant, demetalated, allylated and grafted to acrylated TEMPO through a copolymerization protocol. Then, the chlorophyll monomers were coordinated to Co ions, immobilized on magnetic nanoparticles and the resulting hybrid was used as a powerful catalyst for a variety of oxidation reactions. By using the present method, oxidation of benzylic alcohols and alkyl benzenes to carbonyls was accomplished in water under aerobic conditions. Moreover, direct oxidation of alcohols to carboxylic acids was performed by adding NaOCl to the mixture. All entries were oxidized to the corresponding desired product with high to excellent yields and up to 97% selectivity. The catalyst was thoroughly characterized by CV, TGA, VSM, XRD, XPS, DLS, FE-SEM, TEM, UV-Vis, EDX, and BET analyses. The activity of the catalyst was investigated by applying various components of the catalyst to the oxidation model separately. The reasonable mechanisms are suggested based on the cooperation between the TEMPO groups and cobalt(iii) (or Co(iv)) sites on the catalyst. The catalyst could be recovered and reused for at least 7 consecutive recycles without any considerable reactivity loss. This journal is
- Hamah-Ameen, Baram Ahmed,Kazemnejadi, Milad,Mahmoudi, Boshra,Rostami, Amin
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p. 6600 - 6613
(2020/11/16)
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- Fe3O4@SiO2@Im[Cl]Mn(III)-complex as a highly efficient magnetically recoverable nanocatalyst for selective oxidation of alcohol to imine and oxime
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An efficient and environmentally friendly oxidation process for the one-pot preparation of oxime, imine and carbonyl compounds through alcohol oxidation in the presence of H2O2 and/or O2 have been developed by a melamine-Mn(III) Schiff base complex supported on Fe3O4@SiO2–Cl nanoparticles, named as Fe3O4@SiO2@Im[Cl]Mn(III)-complex nanocomposite, at room temperature. Direct oxidation of alcohol to carboxylic acid was performed using the catalyst in the presence of molecular O2 at room temperature in a different approach. The oxidation products were obtained with excellent yields and high TOFs. The properties of the catalyst were characterized by Fourier transform infrared spectroscopy (FTIR), elemental analysis (C, H, N), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma (ICP), cyclic voltammetry (CV), nuclear magnetic resonance (1H & 13C NMR), vibration sample magnetometer (VSM), Brunauer– Emmett–Teller (BET) and differential pulse voltammetry (DPV) analyses. The mechanism of the oxidation processes was investigated for the both H2O2 and O2 oxidants. The role of the imidazolium moiety in the catalyst as a secondary functionality was investigated. Chemoselectivity behavior of the catalyst was studied by some combinations. The catalyst could be recycled from the reaction mixture by a simple external magnet and reused for several times without any considerable reactivity loss.
- Kazemnejadi, Milad,Alavi, Seyyedeh Ameneh,Rezazadeh, Zinat,Nasseri, Mohammad Ali,Allahresani, Ali,Esmaeilpour, Mohsen
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p. 230 - 249
(2019/03/28)
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- Synthetic method of 4-methoxysalicylic acid
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The invention belongs to the technical field of organic chemical synthesis and discloses a synthetic method of 4-methoxysalicylic acid, comprising the steps of (1) reacting for preparation, to be specific, adding 2,4-dihydroxybenzoic acid into methanol solution of sodium methylate, dropwise adding methyl p-toluenesulfonate, and stirring the reaction solution; (2) distilling, to be specific, distilling the reaction solution of step (1), and removing methanol; (3) acidifying, to be specific, pouring the reaction solution of step (2) into an ice water mixture with hydrochloric acid, and stirring;(4) filtering and cleaning, to be specific, filtering the mixture of step (3), and cleaning with water to obtain crude 4-methoxysalicylic acid. The methyl p-toluenesulfonate having little toxicity isused to replace highly toxic dimethyl sulfate; the sodium methylate is used as a catalyst; few byproducts are produced; the preparation process is simple; little wastewater is generated; light pollution is caused; the prepared 4-methoxysalicylic acid has high purity and high yield.
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Paragraph 0028-0032
(2019/02/13)
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- Ruthenium(II)-Catalyzed C-H Oxygenations of Reusable Sulfoximine Benzamides
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C-H oxygenations of synthetically meaningful sulfoximine benzamides were accomplished by a versatile ruthenium catalysis regime. The ruthenium(II) catalyst was characterized by excellent mono- and chemoselectivity as well as positional selectivity via facile base-assisted intramolecular electrophilic substitution-type (BIES) C-H activation. The synthetic utility of the approach was reflected by high functional group tolerance and sulfoximine removal in a traceless fashion.
- Raghuvanshi, Keshav,Zell, Daniel,Ackermann, Lutz
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supporting information
p. 1278 - 1281
(2017/03/22)
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- Carboxylation of Phenols with CO2 at Atmospheric Pressure
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A convenient and efficient method for the ortho-carboxylation of phenols under atmospheric CO2 pressure has been developed. This method provides an alternative to the previously reported Kolbe-Schmitt method, which requires very high pressures of CO2. The addition of a trisubstituted phenol has proved essential for the successful carboxylation of phenols with CO2 at standard atmospheric pressure, allowing the efficient preparation of a broad variety of salicylic acids.
- Luo, Junfei,Preciado, Sara,Xie, Pan,Larrosa, Igor
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supporting information
p. 6798 - 6802
(2016/05/11)
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- General method for the synthesis of salicylic acids from phenols through palladium-catalyzed silanol-directed C-H carboxylation
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A silanol-directed, palladium-catalyzed C-H carboxylation reaction of phenols to give salicylic acids has been developed. This method features high efficiency and selectivity, and excellent functional-group tolerance. The generality of this method was demonstrated by the carboxylation of estrone and by the synthesis of an unsymmetrically o,o′-disubstituted phenolic compound through two sequential C-H functionalization processes.
- Wang, Yang,Gevorgyan, Vladimir
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p. 2255 - 2259
(2015/02/19)
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- Regioselective ortho-carboxylation of phenols catalyzed by benzoic acid decarboxylases: A biocatalytic equivalent to the Kolbe-Schmitt reaction
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The enzyme catalyzed carboxylation of electron-rich phenol derivatives employing recombinant benzoic acid decarboxylases at the expense of bicarbonate as CO2 source is reported. In contrast to the classic Kolbe-Schmitt reaction, the biocatalytic equivalent proceeded in a highly regioselective fashion exclusively at the ortho-position of the phenolic directing group in up to 80% conversion. Several enzymes were identified, which displayed a remarkably broad substrate scope encompassing alkyl, alkoxy, halo and amino- functionalities. Based on the crystal structure and molecular docking simulations, a mechanistic proposal for 2,6-dihydroxybenzoic acid decarboxylase is presented.
- Wuensch, Christiane,Gross, Johannes,Steinkellner, Georg,Lyskowski, Andrzej,Gruber, Karl,Glueck, Silvia M.,Faber, Kurt
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p. 9673 - 9679
(2014/03/21)
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- PD(II)-CATALYZED HYDROXYLATION OF ARENES WITH O2 OR AIR
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Pd (II) -catalyzed ortho-hydroxylat ion of variously substituted aromatic carboxylic acids under O2 or air is achieved under non-acidic conditions. Extensive labeling studies support a direct oxygenation of aryl C-H bonds with molecular oxygen.
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Page/Page column 14
(2011/04/24)
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- Synthesis of mangiferin, isomangiferin, and homomangiferin
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Mangiferin, isomangiferin, and homomangiferin, the xanthone C-glycosides with a wide spectrum of pharmacological effects, were synthesized concisely, featuring a C-glycosylation of a xanthene derivative with perbenzylglucopyranosyl N-phenyltrifluoroacetimidate.
- Wu, Zhongtao,Wei, Guo,Lian, Gaoyan,Yu, Biao
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scheme or table
p. 5725 - 5728
(2010/10/03)
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- Pd(II)-catalyzed hydroxylation of arenes with 1 atm of O2 or air
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(Chemical Equation Presented) Pd(II)-catalyzed ortho-hydroxylation of variously substituted benzoic acids under 1 atm of O2 or air is achieved under nonacidic conditions. Extensive labeling studies support a direct oxygenation of aryl C-H bonds with molecular oxygen.
- Zhang, Yang-Hui,Yu, Jin-Quan
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supporting information; experimental part
p. 14654 - 14655
(2010/01/06)
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- A convenient procedure for parallel ester hydrolysis
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The treatment of alkyl esters with barium hydroxide octahydrate in methanol followed by protonation with anhydrous hydrogen chloride affords carboxylic acids. The procedure does not require aqueous workup and is particularly suitable for parallel synthesis applications.
- Anderson, Marc O.,Moser, Jamie,Sherrill, John,Guy, R. Kiplin
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p. 2391 - 2393
(2007/10/03)
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- Demethoxylation and hydroxylation of methoxy- and hydroxybenzoic acids by OH-radicals. Processes of potential importance for food irradiation
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The hydroxylation process for methoxy- and hydroxy-benzoic acids (MBA, HBA) induced by γ-radiation is compared. 2-, 3-, and 4-methoxybenzoic acid as well as 3-hydroxybenzoic acid have been irradiated in N2O and aerated solutions up to 1.5 kGy. The products were analyzed by HPLC. The results for 2- and 4-HBA have been taken from literature data. The OH·-adduct distribution is generally the same for the hydroxy- as well as for the methoxy-benzoic acid isomers. With both 4-HBA and 4-MBA more than 65% C3-adducts and about 15% C4-adducts are formed, which could be proved by their reactions with K3 Fe(CN)6. Oxidation of the nonipso-adducts of 3-HBA and 3-MBA results in 84 and 87% of the corresponding phenols. Whereas in N2O-saturated solutions only part of the OH·-radicals leads to substrate decomposition, in the presence of air, the degradation of both kinds of compounds is equivalent to [OH·]. The nonipso OH·-adducts of the HBAs are converted into 68-77% hydroxylation products. With the MBAs, the hydroxylation process is ≤10%. This is attributed to different decay pathways of the peroxyl radicals, intermediates formed by O2 addition to the OH·-adducts. The hydroxyperoxycyclohexadienyl radicals of the HBAs decay mainly by HO2· elimination to the corresponding phenols, those of the MBAs decay predominantly by fragmentation of the benzene ring, yielding to nonidentified aliphatic products. The replacement of -OCH3 by -OH is practically not influenced by the presence of oxygen, it increases in the sequence 3-MBA 4-MBA 2-MBA. For 2-MBA, yields of more than 15% are obtained. Both processes, hydroxylation as well as demethoxylation, might be of importance for the recognition of radiolytical changes in foodstuff.
- Gaisberger,Solar
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p. 394 - 404
(2007/10/03)
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- Regioselective dealkylation of 2-alkoxybenzoic acid and its amide derivatives with aliphatic amines
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The methoxy group of o-anisic acid was cleaved with aliphatic amines in aprotic dipolar solvents. This cleavage reaction was especially smooth when piperazine in dimethylacetamide was used. This method was applicable to a variety of dealkylations of o-alkoxybenzoic acid and ist amide derivatives with high regio-selectivity.
- Nishioka, Hiroyasu,Nagasawa, Masaaki,Yoshida, Kiyoshi
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p. 243 - 246
(2007/10/03)
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- External preparation for skin
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An external preparing for skin comprising one or more than two types of 2-hydroxy benzoic acid derivative and/or salt thereof represented by the following formula: STR1 wherein R is an alkoxy group or alkyl group in the formula. The external preparation for the skin according to the present invention has a suppression effect on melanine generation by inhibition of tyrosinase activity. Accordingly, an excellent bleaching effect based upon the suppression of chromatosis and a high degree of safety can be obtained.
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- Metal Template ortho-Acylation of Phenols. Direct Synthesis of Salicylic Acid Chlorides and Derivatives
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A direct synthesis of salicylic acid chlorides is achieved via "metal-driven" intracomplex acylation of bromomagnesium and aluminum phenoxides with phosgene.Salicylic acids 5 and some derivatives 6, 7 can be obtained by quenching the reaction mixture with convenient reagents.Moreover the reaction of lithium phenylacetylide with 3 provides a new convenient approach to ortho-hydroxyaryl alkynyl ketones like 8.The oriented complex 2, involving the metal phenoxide and phosgene is proposed to account for the ortho-regioselective control of the reaction.
- Sartori, Giovanni,Casnati, Giuseppe,Bigi, Franca,Bonini, Giovanni
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p. 763 - 766
(2007/10/02)
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- Diels-Alder Approaches to Model Compounds Related to Fredericamycin A
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A series of model compounds related to the antitumor and antibiotic compound fredericamycin A has been prepared.Spiro-2,5-dione (2) has been prepared and established as a novel spiro dienophile in the Diels-Alder reaction with 1,3-butadiene, Danishefsky's diene, a triacetoxy-substituted o-quinodimethane, and two isobenzofuran intermediates.Thus, the cycloaddition of 3-cyano-4,5,7-trimethoxy-1(3H)-isobenzofuranone (35) and 2 afforded 4,9-dihydroxy-5,6,8-trimethoxyspiroindene-2,1'-indan>-1,3-dione (38) in 62percent yield.This methodology provides a viable synthetic route to the quinone portion of fredericamycin A that contains the seven requisite oxygens.
- Evans, Jonathan C.,Klix, Russell C.,Bach, Robert D.
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p. 5519 - 5527
(2007/10/02)
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- REACTION OF POTASSIUM SUPEROXIDE WITH 3-NITRO-2-PHENYL-2H-1-BENZOPYRANS AND THEIR DIHYDRO DERIVATIVES
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3-Nitro-2-phenyl-2H-1-benzopyrans on treatment with potassium superoxide in dimethyl sulphoxide are degraded mainly to the corresponding salicylic acids and benzoic acids. Formation of flavonols, as a minor product are also observed. The dihydro derivatives of 3-nitro-2-phenyl-2H-1-benzopyrans are converted to the corresponding flavonols by potassium superoxide in benzene containing 18-crown-6 ether.
- Rao, Takkellapati Sudhakar,Trivedi, Girish Kumar
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p. 2117 - 2124
(2007/10/02)
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- A Diagnostic Cleavage of Aurones and Chalcones with Alkaline Hydrogen Peroxide in the Presence of Triethylbenzylammonium Chloride (TEBA)
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Aurones and chalcones on treatment with alkaline hydrogen peroxide in dioxan in the presence of triethylbenzylammonium chloride (TEBA) undergo facile cleavage to afford arylcarboxylic acids derived from rings A and B.
- Saxena, Shabnam,Makrandi, J. K.,Grover, S. K.
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p. 473 - 477
(2007/10/02)
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- Dye-sensitized Photo-oxygenation of Chalcones
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The dye-sensitized photo-oxygenation of several chalcones has been examined.Some of the chalcones give rise to degradation products while others lead to flavonol formation.A rational explanation for the observations has been proposed.The study may have a significance in the biogenesis of naturally occurring plant polyphenolics.
- Chawla, H. Mohindra,Chakrabarty, Kakoli
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p. 1511 - 1513
(2007/10/02)
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- A New Method for the Degradation of Anthocyanidins, Flavones, Chalcones, and Coumarins
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After transformation into the corresponding chalcone or flavenol acetates anthocyanidins are oxidatively cleaved with ruthenium tetroxide to yield benzoic acid derivatives of the rings A and B.Flavones, chalcones, and coumarins are degradated by the same method.
- Mentlein, Rolf,Vowinkel, Erich,Wolf, Bernd
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p. 401 - 406
(2007/10/02)
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- Electrophilic Catalysis of Sulphate (-SO3-) Group Transfer: Hydrolysis of Salicyl Sulphates assisted by Intramolecular Hydrogen Bonding
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The hydrolysis of substituted salicyl sulphates has been measured over a range of pH values at 70 deg C to obtain kinetic parameters for hydronium ion (kH) and carboxylic acid (kp) calalysis.A Jaffe treatment of the carboxy-catalysis parameter for a range of nuclear substituents yields ρphenol 1.51; ρcarboxy 0 indicates that the carboxy-function does not ionise on going from the ground- to the transition-state, consistent with hydrogen bonding rather than catalysis through proton transfer.The change in 'effective' charge on the phenol oxygen on going from the ground- to the transition-state confirms less build up of negative charge than in the uncatalysed hydrolysis of aryl sulphates.
- Hopkins, Andrew Ramsay,Green, Adam Llywellyn,Williams, Andrew
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p. 1279 - 1284
(2007/10/02)
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- A BIFLAVANONE FROM SEMECARPUS ANACARDIUM
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A new biflavanone, galluflavanone, has been isolated from the alcoholic extract of the nut shells of Semecarpus anacardium.It has been characterized through chemical and spectral data. - Key Word Index: Semecarpus anacardium; Anacardiaceae; biflavanones; 1H NMR and mass spectra; galluflavanone.
- Murthy, S. S. N.
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p. 2636 - 2638
(2007/10/02)
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- Studies on Pitch Problems Caused by Pulping and Bleaching of Tropical Woods. XIV. Chemistry of the Aurone Derivatives at the Conventional Bleaching Stages
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Rengasin (1), which is responsible for the colored specks on a sheet of bleached sulfate pulp from the woods of rengas (Anacardiaceae), was converted into R1 7 having a novel carbon skeleton.A closely related analogue, S1 8, prepared from sulfuretin (2) was used as a model to investigate further conversions under bleaching conditions.Chlorination of S1 8 produced an equilibrium mixture involving compound 9 as a dominant compound.The latter was transformed by the treatment with chlorine dioxide into an orthoquinone (16) via two pathway containing 10 in one and 15 in another.The monomeric quinone (16) immediately dimerized in acidic media to give 20 under the same conditions as above, and the further oligomerization by the process similar to that in dimerization of 16 finally afforded a mixture of colored oligomers 26.
- Ohtani, Yoshito,Sumimoto, Masashi
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p. 613 - 622
(2007/10/02)
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- Flavonoid Epoxides. Part 16. Synthesis and Base-catalysed Rearrangement of Aurone Epoxides
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A number of new aurone epoxides have been synthesised by improved method of alkaline hydrogen peroxide epoxidation of aurones.Flavonols were the main products when the reaction period was prolonged.Aurone epoxides on reaction with base rearranged to flavonols and to aroylcoumaran-3-ones.Aurone epoxides may also be synthesised by the Darzens condensation.
- Brady, Brian A.,Geoghegan, Michael,McMurtey, Kenneth D.,O'Sullian, Ivo W.
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p. 119 - 123
(2007/10/02)
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- Synthesis of 5H-Benzopyranoquinoline-6,12-diones by Photooxidative Cyclisation of Some N-Phenyl-4(H)-oxo-1-benzopyran-2-carboxamides
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N-Phenyl-4(H)-oxo-1-benzopyran-2-carboxamides (Ia-d) on photooxidation in the presence of iodine in benzene by a long wavelength mercury are lamp furnish 5H--benzopyranoquinoline-6,12-diones (IIa-c), the aza structural analogues of the rotenoids.
- Kumar, K. Akshaya,Srimannarayana, G.
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p. 604 - 606
(2007/10/02)
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- The Reaction of 3-Hydroxyflavones with Metal Salts
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The reaction of 3-hydroxyflavones (1a-d) with lead(IV) acetate gave 1,2-diphenylethanediones (2a-d), 1,2-diphenyl-2-hydroxyethanones, 2-hydroxybenzoic acids (7 and 9), and benzoic acids (8 and 10), and the reaction with manganese(III) acetate yielded 2, 7, 8, 9, and 10.In addition to 2, 7, and 10, 6-methoxy-2-(4-methoxybenzoyloxy)-3(2H)-benzofuranone and 2-hydroxy-4-methoxybenzaldehyde were obtained in the reaction of 1c with manganese(III) acetate.It has been established by the studies of 14C-labelled compounds that the C(3) in the 3-hydroxyflavone was lost during the reaction.
- Hamado, Mutsumi,Kurosawa, Kazu
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p. 2630 - 2633
(2007/10/02)
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