- Heterogeneous vanadium-catalyzed oxidative cleavage of olefins for sustainable synthesis of carboxylic acids
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The development of green and sustainable processes to synthesize active pharmaceutical ingredients and key starting materials is a priority for the pharmaceutical industry. A green and sustainable protocol for the oxidative cleavage of olefins to produce pharmaceutically and biologically valuable carboxylic acids is achieved. The developed protocol involves 70% aq. TBHP as an oxidant over a heterogeneous vanadium catalyst system. Notably, the synthesis of industrially important azelaic acid from various renewable vegetable oils is accomplished. The catalyst could be recycled for up to 5 cycles without significant loss in yield and the protocol was successfully demonstrated at the gram-scale.
- Upadhyay, Rahul,Rana, Rohit,Sood, Aakriti,Singh, Vikash,Kumar, Rahul,Srivastava, Vimal Chandra,Maurya, Sushil K.
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supporting information
p. 5430 - 5433
(2021/06/09)
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- Continuous production method of benzoic acid derivative
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The invention relates to the technical field of preparation of benzoic acid derivatives. The invention particularly relates to a continuous production method of a benzoic acid derivative. The continuous reaction device is characterized by comprising a small-diameter sleeve, wherein the small-diameter sleeve is sleeved with a large-diameter sleeve, and a small pipeline is arranged between the small-diameter sleeve and the large-diameter sleeve, and a plurality of small holes are arranged on the small pipeline. The small-diameter casing is rotated, the large-diameter casing is fixed, and the reaction liquid composed of the nitric acid and the toluene derivative is between a small-diameter casing pipe and a large-diameter casing pipe.
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Paragraph 0032-0034
(2021/11/14)
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- Silver-catalyzed decarboxylative homocoupling reaction for the construction of tetrafluoroethylene-bridging aromatic compounds
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The Ag(I)-catalyzed decarboxylative homocoupling from the difluoroacetate has been developed to the synthesis of symmetric CF2–CF2 containing dimers. This radical dimerization overpasses the prefunctionalization of the substrate and provides a direct and efficient method for construction of tetrafluoroethylene bridge-linked homodimers.
- Wang, Yong,Zhao, Huaxin,Xie, Xiaojuan,Jiang, Haizhen,Deng, Hongmei,Hao, Jian,Wan, Wen
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supporting information
p. 2961 - 2970
(2019/08/22)
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- A biocatalytic method for the chemoselective aerobic oxidation of aldehydes to carboxylic acids
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Herein, we present a study on the oxidation of aldehydes to carboxylic acids using three recombinant aldehyde dehydrogenases (ALDHs). The ALDHs were used in purified form with a nicotinamide oxidase (NOx), which recycles the catalytic NAD+ at the expense of dioxygen (air at atmospheric pressure). The reaction was studied also with lyophilised whole cell as well as resting cell biocatalysts for more convenient practical application. The optimised biocatalytic oxidation runs in phosphate buffer at pH 8.5 and at 40 °C. From a set of sixty-one aliphatic, aryl-Aliphatic, benzylic, hetero-Aromatic and bicyclic aldehydes, fifty were converted with elevated yield (up to >99%). The exceptions were a few ortho-substituted benzaldehydes, bicyclic heteroaromatic aldehydes and 2-phenylpropanal. In all cases, the expected carboxylic acid was shown to be the only product (>99% chemoselectivity). Other oxidisable functionalities within the same molecule (e.g. hydroxyl, alkene, and heteroaromatic nitrogen or sulphur atoms) remained untouched. The reaction was scaled for the oxidation of 5-(hydroxymethyl)furfural (2 g), a bio-based starting material, to afford 5-(hydroxymethyl)furoic acid in 61% isolated yield. The new biocatalytic method avoids the use of toxic or unsafe oxidants, strong acids or bases, or undesired solvents. It shows applicability across a wide range of substrates, and retains perfect chemoselectivity. Alternative oxidisable groups were not converted, and other classical side-reactions (e.g. halogenation of unsaturated functionalities, Dakin-Type oxidation) did not occur. In comparison to other established enzymatic methods such as the use of oxidases (where the concomitant oxidation of alcohols and aldehydes is common), ALDHs offer greatly improved selectivity.
- Knaus, Tanja,Tseliou, Vasilis,Humphreys, Luke D.,Scrutton, Nigel S.,Mutti, Francesco G.
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supporting information
p. 3931 - 3943
(2018/09/11)
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- A mild method for synthesizing carboxylic acids by oxidation of aldoximes using hypervalent iodine reagents
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A mild oxidation method for the conversion of aldoximes to carboxylic acids was developed mediated by hypervalent iodine reagents. This method covers a wide range of functionalized aldoximes and proceeds under mild conditions, utilizing PhI(OH)OTs as an oxidant.
- Nakamura, Akira,Kanou, Hodaka,Tanaka, Junki,Imamiya, Akira,Maegawa, Tomohiro,Miki, Yasuyoshi
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supporting information
p. 541 - 544
(2018/02/07)
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- Rational Design of Rod-Like Liquid Crystals Exhibiting Two Nematic Phases
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Recently, a polar, rod-like liquid-crystalline material was reported to exhibit two distinct nematic mesophases (termed N and NX) separated by a weakly first-order transition. Herein, we present our initial studies into the structure–property relationships that underpin the occurrence of the lower-temperature nematic phase, and report several new materials that exhibit this same transformation. We have prepared material with significantly enhanced temperature ranges, allowing us to perform a detailed study of both the upper- and lower-temperature nematic phases by using small-angle X-ray scattering. We observed a continuous change in d spacing rather than a sharp change at the phase transition, a result consistent with a transition between two nematic phases, structures of which are presumably degenerate.
- Mandle, Richard J.,Cowling, Stephen J.,Goodby, John W.
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supporting information
p. 14554 - 14562
(2017/10/23)
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- Synthesis of Psoralidin derivatives and their anticancer activity: First synthesis of Lespeflorin I1
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Synthetic scheme for the preparation of a number of different derivatives of anticancer natural product Psoralidin is described. A convergent synthetic approach is followed using simple starting materials like substituted phenyl acetic esters and benzoic acids. The developed synthetic route leads us to complete the first synthesis of an analogous natural product Lespeflorin I1, a mild melanin synthesis inhibitor. Preliminary bioactivity studies of the synthesized compounds are carried out against two commonly used prostate cancer cell lines. Results show that the bioactivity of the compounds can be manipulated by the simple modification of the functional groups.
- Pahari, Pallab,Saikia, Ujwal Pratim,Das, Trinath Prasad,Damodaran, Chendil,Rohr, Jürgen
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supporting information
p. 3324 - 3334
(2016/05/19)
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- Palladium on carbon-catalyzed aqueous transformation of primary alcohols to carboxylic acids based on dehydrogenation under mildly reduced pressure
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The catalytic dehydrogenation of alcohols to carbonyl products is a green sustainable oxidation with no production of waste except for hydrogen, which can be an energy source. Additionally, a reusable heterogeneous catalyst is valuable from the viewpoint of process chemistry and water is a green solvent. We have accomplished the palladium on carbon (Pd/C)-catalyzed dehydrogenation of primary alcohols to carboxylic acids in water under a mildly reduced pressure (800 hPa). The reduced pressure can be easily controlled by the vacuum controller of the rotary evaporator to remove the excess of generated hydrogen, which causes the reduction (reverse reaction) of aldehydes to alcohols (starting materials) and other undesirable side reactions. The present method is applicable to the reaction of various aliphatic and benzylic alcohols to the corresponding carboxylic acids, and the Pd/C could be reused at least 5 times.
- Sawama, Yoshinari,Morita, Kosuke,Asai, Shota,Kozawa, Masami,Tadokoro, Shinsuke,Nakajima, Junichi,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 1205 - 1210
(2015/04/22)
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- Laccase-Mediator System for Alcohol Oxidation to Carbonyls or Carboxylic Acids: Toward a Sustainable Synthesis of Profens
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By combining two green and efficient catalysts, such as the commercially available enzyme laccase from Trametes versicolor and the stable free radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), the oxidation in water of some primary alcohols to the corresponding carboxylic acids or aldehydes and of selected secondary alcohols to ketones can be accomplished. The range of applicability of bio-oxidation is widened by applying the optimized protocol to the oxidation of enantiomerically pure 2-arylpropanols (profenols) into the corresponding 2-arylpropionic acids (profens), in high yields and with complete retention of configuration.
- Galletti, Paola,Pori, Matteo,Funiciello, Federica,Soldati, Roberto,Ballardini, Alberto,Giacomini, Daria
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p. 2684 - 2689
(2016/12/23)
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- Catalytic transformation of alcohols to carboxylic acid salts and H 2 using water as the oxygen atom source
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The oxidation of alcohols to carboxylic acids is an important industrial reaction used in the synthesis of bulk and fine chemicals. Most current processes are performed by making use of either stoichiometric amounts of toxic oxidizing agents or the use of pressurized dioxygen. Here, we describe an alternative dehydrogenative pathway effected by water and base with the concomitant generation of hydrogen gas. A homogeneous ruthenium complex catalyses the transformation of primary alcohols to carboxylic acid salts at low catalyst loadings (0.2 mol%) in basic aqueous solution. A consequence of this finding could be a safer and cleaner process for the synthesis of carboxylic acids and their derivatives at both laboratory and industrial scales.
- Balaraman, Ekambaram,Khaskin, Eugene,Leitus, Gregory,Milstein, David
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p. 122 - 125
(2013/08/24)
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- Copper-catalyzed methyl esterification reactions via C-C bond cleavage
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The highly effective synthesis of methyl esters from benzylic alcohols, aldehydes, or acids via copper-catalyzed C-C cleavage from tert-butyl hydroperoxide is reported in this paper for the first time. Our protocol is easily accessible and practical, making it a possible supplement for the traditional way.
- Zhu, Yan,Yan, Hong,Lu, Linhua,Liu, Defu,Rong, Guangwei,Mao, Jincheng
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p. 9898 - 9905
(2013/10/22)
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- SnO 2 nanoparticles: Preparation and evaluation of their catalytic activity in the oxidation of aldehyde derivatives to their carboxylic acid and sulfides to sulfoxide analogs
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A variety of aromatic and aliphatic aldehydes were converted to the corresponding carboxylic acid derivatives with 30% H2O2 and tert-butyl hydroperoxide as the oxidant in the presence of a catalytic amount of SnO2 nanoparticles as a precursor. These nanoparticles were also used for the efficient catalytic oxidation of sulfides to sulfoxides using 30% H2O2. The present methodology offers several advantages such as applicability to a wide range of aldehydes/sulfides, convenient work-up, mild reaction conditions as well as good yields and reasonable time of the reactions. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
- Dehbashi, Mohsen,Aliahmad, Mousa,Shafiee, Mohammad Reza Mohammad,Ghashang, Majid
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p. 864 - 872
(2013/08/23)
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- Nickel(II) catalyzed oxidation of aldehyde derivatives to their carboxylic acid or ester analogs
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Diverse aromatic, aliphatic and conjugated aldehydes were converted to the corresponding carboxylic acid or methyl ester derivatives with 30 % H 2O2 as the oxidant in the presence of a catalytic amount of nickel(II) complex as precursor. Ni(II) complex was prepared from the reaction of methyl 2-{3-[(E)-4-oxopent-2-en-2-ylamino]propylamino}cyclopent-1- enecarbodithioate as a tetra-dentate ligand with Ni(II) acetate in 60 % yield and was tested for its catalytic activity in the oxidation reaction. The prepared complex was characterized on the basis of 1H NMR, FT-IR, MASS, and CHN analysis. Aldehydes were oxidized to their corresponding carboxylic acid in acetonitrile as solvent and were converted to methyl esters in methanol as solvent. For all substrates, a considerable rate enhancement was observed. The present methodology offers several advantages such as applicability to a wide range of aldehydes, convenient work-up, mild reaction conditions, and good yields and reasonable time of the reactions. Graphical Abstract: [Figure not available: see fulltext.]
- Esfandiari, Hadi,Jameh-Bozorghi, Saeed,Esmaielzadeh, Sheida,Shafiee, Mohammad Reza Mohammad,Ghashang, Majid
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p. 3319 - 3325
(2013/09/23)
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- Method for estimating SN1 rate constants: Solvolytic reactivity of benzoates
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Nucleofugalities of pentafluorobenzoate (PFB) and 2,4,6-trifluorobenzoate (TFB) leaving groups have been derived from the solvolysis rate constants of X,Y-substituted benzhydryl PFBs and TFBs measured in a series of aqueous solvents, by applying the LFER equation: log k = sf(Ef + Nf). The heterolysis rate constants of dianisylmethyl PFB and TFB, and those determined for 10 more dianisylmethyl benzoates in aqueous ethanol, constitute a set of reference benzoates whose experimental ΔG ? have been correlated with the ΔH? (calculated by PCM quantum-chemical method) of the model epoxy ring formation. Because of the excellent correlation (r = 0.997), the method for calculating the nucleofugalities of substituted benzoate LGs have been established, ultimately providing a method for determination of the SN1 reactivity for any benzoate in a given solvent. Using the ΔG? vs ΔH? correlation, and taking sf based on similarity, the nucleofugality parameters for about 70 benzoates have been determined in 90%, 80%, and 70% aqueous ethanol. The calculated intrinsic barriers for substituted benzoate leaving groups show that substrates producing more stabilized LGs proceed over lower intrinsic barriers. Substituents on the phenyl ring affect the solvolysis rate of benzhydryl benzoates by both field and inductive effects.
- Matic, Mirela,Denegri, Bernard,Kronja, Olga
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supporting information
p. 8986 - 8998,13
(2012/12/12)
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- A new and efficient aerobic oxidation of aldehydes to carboxylic acids with singlet oxygen in the presence of porphyrin sensitizers and visible light
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A new aerobic route is introduced for the oxidation of a variety of aromatic and aliphatic aldehydes to the corresponding carboxylic acid derivatives using molecular oxygen in the presence of tetraphenylporphyrin (H2TPP), tetramesitylporphyrin (H2TMP), tetrakisdichlorophenylporphyrin (H2TDCPP), ZnTPP, and ZnTMP as sensitizers using visible light in an organic solvent. The method has a wide range of applications, does not involve cumbersome work-up, exhibits chemoselectivity, and proceeds under mild reaction conditions. The products are obtained with good conversions and in reasonable reaction times.
- Hajimohammadi, Mahdi,Safari, Nasser,Mofakham, Hamid,Shaabani, Ahmad
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experimental part
p. 4061 - 4065
(2010/08/07)
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- COMPOUNDS WITH 7-MEMBER CYCLE AND THE PHARMACEUTICAL USE THEREOF FOR PREVENTING AND TREATING DIABETES AND METABOLISM SYNDROME
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The invention discloses a new use of a class of heptacyclic compounds in the preparation of formulations for the prevention and treatment of diabetes and metabolic syndromes; the present invention also discloses a new class of heptacyclic compounds; the present invention also discloses a process for preparing the heptacyclic compounds and a composition containing the same. The heptacyclic compounds of the present invention can be used to effectively preventing or treating diseases such as diabetes and metabolic syndromes.
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Page/Page column 33
(2010/07/06)
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- Synthesis of (E)-stilbenes and (E,E)-1,4-diphenylbuta-1,3-diene promoted by boron trifluoride-diethyl ether complex
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An efficient, simple, and practical method has been de-veloped to regioselectively synthesize (E)-stilbenes and (E,E)-1,4diphenylbuta-1,3-diene in good to excellent yields in the presence of boron trifluoride-diethyl ether complex as a catalyst in a short reaction (30-60 s) at room temperature. Georg Thieme Verlag Stuttgart.
- Narender,Papi Reddy,Madhur
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experimental part
p. 3791 - 3796
(2010/03/04)
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- Silver nitrate-catalyzed oxidation of aldehydes to carboxylic acids by H2O2
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A variety of aromatic, aliphatic and conjugated aldehydes were converted to the corresponding carboxylic acid derivatives with 30% H2O 2 as the oxidant in the presence of catalytic amounts of AgNO 3. The method described has wide range of applicabilities, does not involve cumbersome work-up, exhibits chemoselectivity and proceeds under mild reaction conditions, and the resulting products are obtained in good yields within reasonable time.
- Chakraborty, Debashis,Gowda, Ravikumar R.,Malik, Payal
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experimental part
p. 6553 - 6556
(2011/02/21)
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- Alternatives to N,N-diethyl-2,4-dimethoxybenzamide as a precursor for the synthesis of 6,8-dimethoxy-3-methyl-3,4-dihydro-1H-isochromen-1-one
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Although the amide group of N,N-diethyl-2,4-dimethoxybenzamide facilitates directed ortho-metallation and subsequent allylation of the aromatic ring, it is not readily hydrolyzed prior to conversion into the title isochromenone. This article describes the use of 1-(2-allyl-4,5-dimethoxybenzoyl)-4-methylpiperazine and N,N-diethyl-2-(2-hydroxypropyl)-4,6-dimethoxybenzamide as alternative substrates for conversion into 6,8-dimethoxy-3-methyl-3,4-dihydro-1H-isochromen- 1-one. Copyright Taylor & Francis Group, LLC.
- Van Otterlo, Willem A. L.,Michael, Joseph P.,De Koning, Charles B.
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p. 3611 - 3621
(2008/03/14)
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- Carboxylation of anisole derivatives with CO and O2 catalyzed by Pd(OAc)2 and molybdovanadophosphates
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Anisole and its homologues were carboxylated under the influence of CO and O2 catalyzed by Pd(OAc)2 combined with molybdovanadophosphates (HPMoV) under mild conditions to give the corresponding carboxylic acids in fair to good yields; for instance, anisole underwent the carboxylation under a mixed gas of CO (0.5 atm) and O2 (0.5 atm) in the presence of Pd(OAc)2 (5 mol%) and H5PMo 10V2O40·nH2O (2 mol%) to form an isomeric mixture of anisic acids in good yield.
- Ohashi, Shinichiro,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 486 - 488
(2008/09/18)
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- NOVEL BENSOPHENONE DERIVATIVES OR SALTS THEREOF
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A benzophenone derivative represented by the following formula: whereinR1 represents, for example, an optionally substituted heterocyclic group, or a substituted phenyl group; Z represents, for example, an alkylene group; R2 represents, for example, a carboxyl group optionally protected with alkyl;R3 represents, for example, an optionally protected hydroxyl group; R4 represents, for example, an optionally substituted cycloalkyloxy group; and R5 represents, for example, a hydrogen atom, ???or a salt thereof has anti-arthritic activity, inhibits bone destruction caused by arthritis, and provides high safety and excellent pharmacokinetics and thus is useful as therapeutic agent for arthritis. These compounds have inhibitory effect on AP-1 activity and are useful as preventive or therapeutic agent for diseases in which excessive expression of AP-1 is involved.
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- π-deficient 2-(arylsulfonyl)ethyl esters as protecting groups for carboxylic acids
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Several π-deficient 2-(arylsulfonyl)ethyl groups have been studied as carboxylic acid protecting groups. The 2-[3,5-bis(trifluoromethyl)phenylsulfonyl]ethyl group is the most easily removed protecting group for acids under mild basic conditions using aqueous NaHCO3.
- Alonso, Diego A.,Nájera, Carmen,Varea, Montserrat
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p. 277 - 287
(2007/10/03)
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- Synergistic compositions for the selective control of tumor tissue
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According to the invention, compositions are made available which have a strong cytotoxic effect which is largely selective on tumor tissue. The invention is based on the fact that certain benzoic acid derivatives have a strong synergistic effect as a mixture and destroy cancer cells selectively in a pH range of 7 or below, such as from 6.5 to 7.
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- Synergistically acting compositions for selectively combating tumor tissue
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According to the invention, compositions are made available which have a strong cytotoxic effect which is largely selective on tumor tissue. The invention is based on the fact that certain benzoic acid derivatives have a strong synergistic effect as a mixture and destroy cancer cells selectively in a pH range of 7 or below, such as from 6.5 to 7.
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- Radical-capturing reaction of 5,7,3′,4′-tetramethylquercetin with the AIBN radical initiator
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In order to clarify the mechanism for the radical-capturing reaction which is initiated at the C3-hydroxyl group of flavonols, 5,7,3′,4′-tetramethylquercetin (TMQ) was reacted with the 2,2′-azobis-isobutyronitrile (AIBN) radical initiator in benzene. Six products, one depside and its two hydrolytic products, one nitrite adduct, and two others, were isolated from the reaction mixture, and their structures were determined by instrumental analyses. The quantitative change to the four main products against the reaction time was measured by an HPLC method. The radical-capturing reaction pathway for TMQ with AIBN is proposed from these products and their quantitative changes. The pathway dividing into two clearly reveals that one subpath formed the depside and its hydrolytic products, while the other formed the nitrite adduct. The reactivity of each two sub-path was nearly the same, different from the case of TMQ and the 2,2′-azobis-2,4-dimethylvaleronitrile (AMVN) radical initiator.
- Ishikawa, Takahiro,Takagi, Michiyo,Kanou, Mamiko,Kawai, Shingo,Ohashi, Hideo
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p. 173 - 177
(2007/10/03)
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- 2-(2-aminophenyl)-acetaldehyde dimethyl acetal: A novel reagent for the protection of carboxylic acids
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The synthesis and use of 2-(2-aminophenyl)-acetaldehyde dimethyl acetal 1 are described. The amides 2, derived from this amine and carboxylic acids, are stable under basic conditions and thus can be regarded as the protected carboxylic acids. The corresponding carboxylic acids are regenerated by conversion of 2 into indolylamides 3 by treatment with CSA and subsequent hydrolysis with LiOOH or NaOH. In addition, 3 can be easily converted to esters, amides, and aldehydes.
- Arai, Eri,Tokuyama, Hidetoshi,Linsell, Martin S.,Fukuyama, Tohru
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- Cysteamine derivatives and antirheumatic agents containing cysteamine derivatives
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A cysteamine derivative represented by general formula (I): STR1 wherein R1 represents a straight-chain or a branched alkyl radical having 1 to 6 carbon atoms, R2 represents hydrogen atom or n-propyl radical, and X represents a radical selected from the group consisting of radicals containing cysteamine moiety (N S) represented by formula (II): STR2 formula (III): STR3 formula (IV): STR4 formula (V): STR5 or formula (VI): STR6 wherein R2 represents hydrogen atom or a straight-chain or a branched alkyl group having 1 to 10 carbon atoms is provided. The cysteamine derivative is effective as an antirheumatic agent.
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- 5-HYDROXY-7,8,2',4'-TETRAMETHOXYFLAVONE FROM LIMNOPHILA RUGOSA
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The petrol extract of the aerial parts and roots of limnophila rugosa yielded a new flavone, 5-hydroxy-7,8,2',4'-tetramethoxyflavone Key Word Indx - Limnophila rugosa; Scropulariaceae; 5-hydroxy-7,8,2',4'-tetramethoxyflavone.
- Mukherjee, K. S.,Chakraborty, C. K.,Chatterjee, T. P.
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p. 1778 - 1779
(2007/10/02)
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- Manganese(III)-Mediated Formylation of Aromatic Compounds in the Presence of Malonic Acid
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The reaction of naphthlenes with malonic acid in the presence of manganese(III) acetate gives naphthalenecarbaldehydes and naphthalenecarboxylic acids.Similar reactions of anthracene, pyrene, and methoxybenzenes also yield formylated and carboxylated products.It was found that the formyl group introduced to the aromatic ring was not derived from carboxymethyl radical generated directly by the thermolysis of manganese(III) acetate, but from a dicarboxymethyl radical formed by the interaction of malonic acid and manganese(III) acetate.In addition, it was also found that the dicarboxymethyl radicals attacked the position of the highest electron density on the aromatic ring and that this formylation was effective when the ionization potential of the aromatic copound was lower than 7.8 eV.
- Nishino, Hiroshi,Tsunoda, Katsunori,Kurosawa, Kazu
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p. 545 - 550
(2007/10/02)
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- 5-Substituted pyrazolo[4,3-d]pyrimidine-7-ones and methods of use
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The present invention relates to novel 5-substituted pyrazolo[4,3-d]pyrimidine-7-one compounds, and compositions, methods of use and processes to make therefor. The novel compounds are useful in the treatment of cardiovascular disorders, such as heart failure or cardiac insufficiency. The novel compounds bind adenosine receptors and selectively inhibit phosphodiesterase.
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- 2,4,2'-TRIHYDROXY-4'-METHOXYBENZIL FROM ZOLLERNIA PARAENSIS
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A new phenolic compound, isolated from the wood of Zollernia paraensis, has been shown to be 2,4,2'-trihydroxy-4'-methoxybenzil by spectral data and synthesis.Key Word Index -Zollernia paraensis, Leguminosae; 2,4,2'-trihydroxy-4'-methoxybenzil.
- Ferrari, F.,Lima, R. Alves De,Bettolo, G. B. Marini
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p. 2691 - 2692
(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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- 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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- NEW PRENYLATED ISOFLAVONES FROM MILLETTIA PACHYCARPA
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Isolation of four new isoflavones from a new collection of Millettia pachycarpa is reported.Proof of the structure of lupinifolol, previously isolated from M. pachycarpa, by synthesis of dehydrolupinifolol is described.Key Word Index- Millettia pachycarpa; Leguminosae; Lotodoideae; prenylated isoflavones.
- Singhal, Ashok K.,Sharma, Ram P.,Madhusudanan, K. P.,Thyagarajan, Gopalakrishna,Herz, Werner,Govindan, Serengolam V.
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p. 803 - 806
(2007/10/02)
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- METALATION REACTIONS. VI. STERIC LIMITS IN THE PREPARATION OF 1,2,3-TRI-SUBSTITUTED BENZENE DERIVATIVES
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Metalation of 1,3-dialkoxy-, 1-alkoxy-3-(alkylthio)- and 1,3-bis-(alkylthio)-benzenes with n-butyllithium has been examined to verify the possibility of preparing 1,2,3-tri-substituted benzene derivatives.The reaction is affected by steric hindrance.The yields of the metalation in the position ortho to both the substituents decrease as steric requirement increases becoming zero when the bulk of both the alkyl substituent and the hetero-atom is increased.It has been shown that synthesis of 1,2,3-tri-substituted derivatives by this route is feasible only with small substituents.
- Cabiddu, Salvatore,Maccioni, Antonio,Piras, Pier Paolo,Plumitallo, Antonio
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p. 123 - 128
(2007/10/02)
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