- A highly reactive P450 model compound I
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(Graph Presented) The detection and kinetic characterization of a cytochrome P450 model compound I, [OFeIV-4-TMPyP]+ (1), in aqueous solution shows extraordinary reaction rates for C-H hydroxylations. Stopped-flow spectrophotometric monitoring of the oxidation of Fe III-4-TMPyP with mCPBA revealed the intermediate 1, which displays a weak, blue-shifted Soret band at 402 nm and an absorbance at 673 nm, typical of a porphyrin π-radical cation. This intermediate was subsequently transformed into the well-characterized OFeIV-4-TMPyP. Global analysis afforded a second-order rate constant k1 = (1.59 ± 0.06) × 10 7 M-1 s-1 for the formation of 1 followed by a first-order decay with k2 = 8.8 ± 0.1 s-1. 1H and 13C NMR determined 9-xanthydrol to be the major product (~90% yield) of xanthene oxidation by 1. Electrospray ionization mass spectrometry carried out in 47.5% 18OH2 indicated 21% 18O incorporation, consistent with an oxygen-rebound reaction scenario. Xanthene/xanthene-d2 revealed a modest kinetic isotope effect, kH/kD = 2.1. Xanthene hydroxylation by 1 occurred with a very large second-order rate constant k3 = (3.6 ± 0.3) × 106 M-1 s-1. Similar reactions of fluorene-4-carboxylic acid and 4-isopropyl- and 4-ethylbenzoic acid also gave high rates for C-H hydroxylation that correlated well with the scissile C-H bond energy, indicating a homolytic hydrogen abstraction transition state. Mapping the observed rate constants for C-H bond cleavage onto the Bronsted- Evans-Polanyi relationship for similar substrates determined the H-OFe IV-4-TMPyP bond dissociation energy to be ~100 kcal/mol. The high kinetic reactivity observed for 1 is suggested to result from a high porphyrin redox potential and spin-state-crossing phenomena. More generally, subtle charge modulation at the active site may result in high reactivity of a cytochrome P450 compound I.
- Bell, Seth R.,Groves, John T.
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- Meso-Substitution Activates Oxoiron(IV) Porphyrin π-Cation Radical Complex More Than Pyrrole-β-Substitution for Atom Transfer Reaction
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There have been two known categories of porphyrins: a meso-substituted porphyrin like meso-tetramesitylporphyrin (TMP) and a pyrrole-β-substituted porphyrin like native porphyrins and 2,7,12,17-tetramethyl-3,8,13,18-tetramesitylporphyrin (TMTMP). To reveal the chemical and biological function of native hemes, we compare the reactivity of the oxoiron(IV) porphyrin π-cation radical complex (Compound I) of TMP (TMP-I) with that of TMTMP (TMTMP-I) for epoxidation, hydrogen abstraction, hydroxylation, sulfoxidation, and demethylation reactions. Kinetic analysis of these reactions indicated that TMP-I is much more reactive than TMTMP-I when the substrate is not sterically bulky. However, as the substrate is sterically bulkier, the difference of the reactivity between TMP-I and TMTMP-I becomes smaller, and the reactivity of TMP-I is comparable to that of TMTMP-I for a sterically hindered substrate. Since the redox potential of TMP-I is almost the same as that of TMTMP-I, we conclude that TMP-I is intrinsically more reactive than TMTMP-I for these atom transfer reactions, but the steric effect of TMP-I is stronger than that of TMTMP-I. This is contrary to the previous result for the single electron transfer reaction: TMTMP-I is faster than TMP-I. DFT calculations indicate that the orbital energies of the Fe=O moiety for TMTMP-I are higher than those for TMP-I. The difference in steric effect between TMP-I and TMTMP-I is explained by the distance from the mesityl group to the oxo ligand of Compound I. Significance of the pyrrole-β-substituted structure of the hemes in native enzymes is also discussed on the basis of this study.
- Fukui, Nami,Ueno, Kanako,Hada, Masahiko,Fujii, Hiroshi
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supporting information
p. 3207 - 3217
(2021/03/01)
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- Manganese(Ⅲ)-iodosylbenzene complex, preparation method thereof and oxidant comprising the same
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The present invention relates to a manganese(III)-iodosylbenzene complex, a preparation method thereof, and an oxidant comprising the same. The manganese(III)-iodosylbenzene complex provided in one aspect of the present invention has an effect of inducing a hydrogen atom abstraction (HAA) reaction of cyclohexadiene, dihydroanthracene and xanthine, and an oxygen atom transfer (OAT) reaction of thioanisole and stilbene with excellent electrophilic reactivity. The manganese(III)-iodosylbenzene complex is represented by a compound of formula 1: [Mn^III(L)(OIPh)(OH)]^2+.COPYRIGHT KIPO 2020
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Paragraph 0130-0136; 0141; 0166
(2020/09/22)
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- Asymmetric synthesis of (2S,3S)-3-Me-glutamine and (R)-allo-threonine derivatives proper for solid-phase peptide coupling
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Practical new routes for preparation of (2S,3S)-3-Me-glutamine and (R)-allo-threonine derivatives, the key structural components of cytotoxic marine peptides callipeltin O and Q, suitable for the Fmoc-SPPS, were developed. (2S,3S)-Fmoc-3-Me-Gln(Xan)-OH was synthesized via Michael addition reactions of Ni (II) complex of chiral Gly-Schiff base; while Fmoc-(R)-allo-Thr-OH was prepared using chiral Ni (II) complex-assisted α-epimerization methodology, starting form (S)-Thr(tBu)-OH.
- Tokairin, Yoshinori,Soloshonok, Vadim A.,Moriwaki, Hiroki,Konno, Hiroyuki
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p. 419 - 432
(2018/11/27)
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- CoI-Catalyzed Barbier Reactions of Aromatic Halides with Aromatic Aldehydes and Imines
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The reductive Barbier coupling of aromatic halides and electrophiles has been achieved using a CoBr2/1,10-phenanthroline catalytic system and over stoichiometric amounts of zinc. The reaction displayed a broad scope of substrates, including (hetero)aryl chlorides as pro-nucleophiles and aldehydes or imines as electrophiles, leading to diarylmethanols and diarylmethylamines in moderate to excellent yields, respectively.
- Presset, Marc,Paul, Jér?me,Cherif, Ghania Nait,Ratnam, Nisanthan,Laloi, Nicolas,Léonel, Eric,Gosmini, Corinne,Le Gall, Erwan
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supporting information
p. 4491 - 4495
(2019/02/27)
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- Preparation method of xanthydrol
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The invention relates to the chemical field, in particular to a preparation method of xanthydrol. The method comprises the steps as follows: 31.3 g of o-chlorobenzoic acid, 37.6 g of phenol, 5.53 g ofpotassium carbonate, 16.2 mL of pyridine, 2 g of copper powder, 2 g of cuprous iodide and 200 mL of water are added to a 500 mL three-neck flask, the mixture is stirred mechanically, subjected to reflux for 2 h and cooled to the room temperature, diluted hydrochloric acid is added to make a reaction solution to be acid, a solid is filtered out, washed and dissolved in a 10% sodium hydroxide aqueous solution, the obtained solution is added to a mixed solution of acetic acid and water for precipitation of a solid, the obtained solid is recrystallized with the mixed solution of acetic acid and water, and 36.4 g of white crystal o-phenoxybenzoic acid is obtained; 20 g of o-phenoxybenzoic acid and 80 mL of tetrahydrofuran are added to a 150 mL three-neck flask, the mixture is stirred mechanically and cooled to 0 DEG C, 23 mL of a catalyst is dropwise added at the temperature of 0 DEG C, the obtained mixture is heated for reflux for 30 min after addition and cooled to the room temperature,and ice water is added to a reaction solution. The technological process is simple and safe to operate, the production cost is reduced, environmental pollution is avoided in the reaction process, andthe product quality is improved.
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Paragraph 0008; 0009
(2018/03/26)
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- Earth-Abundant Mixed-Metal Catalysts for Hydrocarbon Oxygenation
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The oxygenation of aliphatic and aromatic hydrocarbons using earth-abundant Fe and Cu catalysts and "green" oxidants such as hydrogen peroxide is becoming increasingly important to atom-economical chemical processing. In light of this, we describe that dinuclear CuII complexes of pyrrolic Schiff-base macrocycles, in combination with ferric chloride (FeCl3), catalyze the oxygenation of π-activated benzylic substrates with hydroperoxide oxidants at room temperature and low loadings, representing a novel design in oxidation catalysis. Mass spectrometry and extended X-ray absorption fine structure analysis indicate that a cooperative action between CuII and FeIII occurs, most likely because of the interaction of FeCl3 or FeCl4- with the dinuclear CuII macrocycle. Voltammetric measurements highlight a modulation of both CuII and FeIII redox potentials in this adduct, but electron paramagnetic resonance spectroscopy indicates that any Cu-Fe intermetallic interaction is weak. High ketone/alcohol product ratios, a small reaction constant (Hammett analysis), and small kinetic isotope effect for H-atom abstraction point toward a free-radical reaction. However, the lack of reactivity with cyclohexane, oxidation of 9,10-dihydroanthracene, oxygenation by the hydroperoxide MPPH (radical mechanistic probe), and oxygenation in dinitrogen-purge experiments indicate a metal-based reaction. Through detailed reaction monitoring and associated kinetic modeling, a network of oxidation pathways is proposed that includes "well-disguised" radical chemistry via the formation of metal-associated radical intermediates.
- Pankhurst, James R.,Curcio, Massimiliano,Sproules, Stephen,Lloyd-Jones, Guy C.,Love, Jason B.
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supporting information
p. 5915 - 5928
(2018/05/28)
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- Structure and Reactivity of a Mononuclear Nonheme Manganese(III)-Iodosylarene Complex
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Transition metal-iodosylarene complexes have been proposed to be key intermediates in the catalytic cycles of metal catalysts with iodosylarene. We report the first X-ray crystal structure and spectroscopic characterization of a mononuclear nonheme manganese(III)-iodosylarene complex with a tetradentate macrocyclic ligand, [MnIII(TBDAP)(OIPh)(OH)]2+ (2). The manganese(III)-iodosylarene complex is capable of conducting various oxidation reactions with organic substrates, such as C-H bond activation, sulfoxidation and epoxidation. Kinetic studies including isotope labeling experiments and Hammett correlation demonstrate the electrophilic character on the Mn-iodosylarene adduct. This novel intermediate would be prominently valuable for expanding the chemistry of transition metal catalysts.
- Jeong, Donghyun,Ohta, Takehiro,Cho, Jaeheung
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supporting information
p. 16037 - 16041
(2018/12/13)
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- Synthetic method of xanthene-9-formic acid
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The invention discloses a synthetic method of xanthene-9-formic acid, which belongs to the field of chemical synthesis. The method comprises the following steps: xanthone is taken as a raw material, then is reduced to xanthydrol under alkaline condition by zinc dust, then the xanthydrol is subjected to a halogenated reaction to obtain the halogenated xanthene, then under effect of a catalyst, a cyanidation reaction is generated to obtain 9-cyan xanthene, through alkali hydrolysis, organic impurity is removed through extraction of an organic solvent, a xanthene-9-formate aqueous solution is obtained, and a xanthene-9-formic acid product is obtained through a neutralization reaction. The method has the advantages of simple operation and safe technology, the xanthene-9-formic acid with high purity is obtained without refining, and the method is easy and effective for industrial production.
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Paragraph 0035; 0036; 0037; 0044; 0045; 0046
(2017/12/09)
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- Thioether compounds and synthetic method thereof
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The invention discloses thioether compounds and a synthetic method thereof. The structure of the thioether compounds is shown in formula I, wherein X and R1-R10 are defined in the specification. According to the synthetic route, a product is finally synthesized from 9H-Xxanthene-9-one through hydrogenation, thio-etherification, hydrogen removal and alkylation. The thioether compounds can have a certain trigger action in radical polymerization and can be subjected to a reversible coupling-cleavage reaction with chain propagation radicals, so that the chain propagation radicals form dormant species, and polymerization shows certain controllability. Meanwhile, compared with reagents used in the traditional 'active'-controllable radical polymerization system, the compounds have the advantages of being nontoxic, odorless, colorless and free of metal ions, have better solubility without additional ligands and the like, and have better application prospect in the field of radical polymerization.
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Paragraph 0036
(2017/08/29)
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- Probe-dependent negative allosteric modulators of the long-chain free fatty acid receptor FFA4
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High-affinity and selective antagonists that are able to block the actions of both endogenous and synthetic agonists of G protein-coupled receptors are integral to analysis of receptor function and to support suggestions of therapeutic potential. Although there is great interest in the potential of free fatty acid receptor 4 (FFA4) as a novel therapeutic target for the treatment of type II diabetes, the broad distribution pattern of this receptor suggests it may play a range of roles beyond glucose homeostasis in different cells and tissues. To date, a single molecule, 4-methyl- N-9H-xanthen-9-yl-benzenesulfonamide (AH-7614), has been described as an FFA4 antagonist; however, its mechanism of antagonism remains unknown. We synthesized AH-7614 and a chemical derivative and demonstrated these to be negative allosteric modulators (NAMs) of FFA4. Although these NAMs did inhibit FFA4 signaling induced by a range of endogenous and synthetic agonists, clear agonist probe dependence in the nature of allosteric modulation was apparent. Although AH-7614 did not antagonize the second long-chain free fatty acid receptor, free fatty acid receptor 1, the simple chemical structure of AH-7614 containing features found in many anticancer drugs suggests that a novel close chemical analog of AH-7614 devoid of FFA4 activity, 4-methyl-N-(9H-xanthen-9-yl)benzamide (TUG-1387), will also provide a useful control compound for future studies assessing FFA4 function. Using TUG-1387 alongside AH-7614, we show that endogenous activation of FFA4 expressed by murine C3H10T1/2 mesenchymal stem cells is required for induced differentiation of these cells toward a more mature, adipocyte-like phenotype.
- Watterson, Kenneth R.,Hansen, Steffen V.F.,Hudson, Brian D.,Alvarez-Curto, Elisa,Raihan, Sheikh Zahir,Azevedo, Carlos M.G.,Martin, Gabriel,Dunlop, Julia,Yarwood, Stephen J.,Ulven, Trond,Milligan, Graeme
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p. 630 - 641
(2017/05/22)
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- Direct coupling reaction of diaryl methanol with ketones or aldehydes catalyzed by AlCl3
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A novel coupling reaction of diaryl methanols with ketones or aldehydes has been developed under the catalysis of AlCl3. Various ketones and aldehydes could couple with 9H-xanthen-9-ol smoothly, affording coupling products in 48%-88% yields. A plausible mechanism using AlCl3 to activate both diaryl methanol and ketone or aldehyde is proposed.
- Zhu, Zhiqiang,Bai, Peng,Wang, Tiantian,Huang, Zhizhen
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supporting information
p. 1176 - 1182
(2015/01/16)
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- Factors affecting hydrogen-tunneling contribution in hydroxylation reactions promoted by oxoiron(IV) porphyrin π-cation radical complexes
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Hydrogen atom transfer with a tunneling effect (H-tunneling) has been proposed to be involved in aliphatic hydroxylation reactions catalyzed by cytochrome P450 and synthetic heme complexes as a result of the observation of large hydrogen/deuterium kinetic isotope effects (KIEs). In the present work, we investigate the factors controlling the H-tunneling contribution to the H-transfer process in hydroxylation reaction by examining the kinetics of hydroxylation reactions at the benzylic positions of xanthene and 1,2,3,4-tetrahydronaphthalene by oxoiron(IV) 5,10,15,20-tetramesitylporphyrin π-cation radical complexes ((TMP+?)FeIVO(L)) under single-turnover conditions. The Arrhenius plots for these hydroxylation reactions of H-isotopomers have upwardly concave profiles. The Arrhenius plots of D-isotopomers, clear isosbestic points, and product analysis rule out the participation of thermally dependent other reaction processes in the concave profiles. These results provide evidence for the involvement of H-tunneling in the rate-limiting H-transfer process. These profiles are simulated using an equation derived from Bells tunneling model. The temperature dependence of the KIE values (kH/kD) determined for these reactions indicates that the KIE value increases as the reaction temperature becomes lower, the bond dissociation energy (BDE) of the C-H bond of a substrate becomes higher, and the reactivity of (TMP+?)FeIVO(L) decreases. In addition, we found correlation of the slope of the ln(kH/kD) - 1/T plot and the bond strengths of the Fe=O bond of (TMP+?)FeIVO(L) estimated from resonance Raman spectroscopy. These observations indicate that these factors modulate the extent of the H-tunneling contribution by modulating the ratio of the height and thickness of the reaction barrier.
- Cong, Zhiqi,Kinemuchi, Haruki,Kurahashi, Takuya,Fujii, Hiroshi
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supporting information
p. 10632 - 10641
(2015/02/19)
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- Synergistic effect of ketone and hydroperoxide in Bronsted acid catalyzed oxidative coupling reactions
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Waste not wasted: A mechanistic study of the autoxidative coupling of xanthene with cyclopentanone uncovered an autoinductive effect of the waste product hydrogen peroxide. It generates radicals in the presence of acid and ketones, which accelerate the reaction by providing an additional pathway to the reactive hydroperoxide intermediate. This discovery could be applied to achieve other Bronsted acid catalyzed oxidative coupling reactions.
- Schweitzer-Chaput, Bertrand,Sud, Abhishek,Pinter, Aron,Dehn, Stefanie,Schulze, Philipp,Klussmann, Martin
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supporting information
p. 13228 - 13232
(2014/01/06)
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- Chemo- and regioselective direct hydroxylation of arenes with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
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Peroxide in, phenol out: The catalyst [-PW10O38V 2(μ-OH)2]3- showed high activity in the hydroxylation of various aromatic compounds with aqueous H2O 2. The system was regioselective, producing para-phenols from monosubstituted benzene derivatives. Furthermore, alkylarenes with reactive side-chain Ca spa 3-H bonds could be chemoselectively hydroxylated without significant formation of side-chain oxygenated products. Copyright
- Kamata, Keigo,Yamaura, Taiyo,Mizuno, Noritaka
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supporting information; experimental part
p. 7275 - 7278
(2012/08/28)
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- A high-valent iron-oxo corrolazine activates C-H bonds via hydrogen-atom transfer
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Oxidation of the FeIII complex (TBP8Cz)Fe III [TBP8Cz = octakis(4-tert-butylphenyl)corrolazinate] with O-atom transfer oxidants under a variety of conditions gives the reactive high-valent Fe(O) complex (TBP8Cz+?)Fe IV(O) (2). The solution state structure of 2 was characterized by XAS [d(Fe-O) = 1.64 A]. This complex is competent to oxidize a range of C-H substrates. Product analyses and kinetic data show that these reactions occur via rate-determining hydrogen-atom transfer (HAT), with a linear correlation for log k versus BDE(C-H), and the following activation parameters for xanthene (Xn) substrate: ΔH? = 12.7 ± 0.8 kcal mol -1, ΔS? = -9 ± 3 cal K-1 mol-1, and KIE = 5.7. Rebound hydroxylation versus radical dimerization for Xn is favored by lowering the reaction temperature. These findings provide insights into the factors that control the intrinsic reactivity of Compound I heme analogues.
- Cho, Kevin,Leeladee, Pannee,McGown, Amanda J.,Debeer, Serena,Goldberg, David P.
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experimental part
p. 7392 - 7399
(2012/06/16)
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- Reaction of benzyne with formamides and acetylimidazole
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The reaction of DMF with o-trimethylsilylphenyl triflate in the presence of CsF afforded dimethyldiphenylammonium triflate, xanthene, and xanthone in 62%, 16%, and 24% yields, respectively. On the other hand, the reaction of dimethylthioformamide with triflate and CsF resulted in diphenyl sulfide, xanthene, and xanthone in 62%, 10%, and 12% yields, respectively. The reaction of acetylimidazole with benzyne gave 9-N,N-diphenylaminoanthracene in 85% yield.
- Okuma, Kentaro,Nojima, Akiko,Nakamura, Yuki,Matsunaga, Nahoko,Nagahora, Noriyoshi,Shioji, Kosei
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experimental part
p. 328 - 332
(2011/05/14)
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- Characterization of tunable piperidine and piperazine carbamates as inhibitors of endocannabinoid hydrolases
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Monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH) are two enzymes from the serine hydrolase superfamily that degrade the endocannabinoids 2-arachidonoylglycerol and, anandamide, respectively. We have recently discovered that, MAGL and, FAAH are both inhibited by carbamates bearing an N-piperidine/piperazine group. Piperidine/piperazine carbamates show excellent in vivo activity, raising brain endocannabinoid levels and producing CB1-dependent behavioral effects in mice, suggesting that they represent a promising class of inhibitors for studying the endogenous functions of MAGL and FAAH. Herein, we disclose a full account of the syntheses, structure-activity relationships, and, inhibitory activities of piperidine/piperazine carbamates against members of the serine hydrolase family. These scaffolds can be tuned for MAGL-selective or dual MAGL-FAAH inhibition by the attachment of an, appropriately substituted bisarylcarbinol or aryloxybenzyl moiety, respectively, on the piperidine/piperazine ring. Modifications to the piperidine/piperazine ring ablated inhibitory activity, suggesting a strict requirement for a six-membered ring to maintain potency.
- Long, Jonathan Z.,Jin, Xin,Adibekian, Alexander,Li, Weiwei,Cravatt, Benjamin F.
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experimental part
p. 1830 - 1842
(2010/08/19)
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- Organocatalytic asymmetric alkylation of aldehydes by SNreaction of alcohols
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Work-alcoholic! The elusive enantioselective catalytic α-alkylation of aldehydes, a widely sought transformation, was brought to execution by the use of alcohols capable of forming stabilized carbocations (see scheme, TFA=trifluoroacetic acid).
- Cozzi, Pier Giorgio,Benfatti, Fides,Zoli, Luca
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supporting information; experimental part
p. 1313 - 1316
(2009/06/30)
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- Reaction of benzyne with salicylaldehydes: General synthesis of xanthenes, xanthones, and xanthols
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The reaction of salicylaldehydes with benzyne prepared from o-trimethylsilyphenyl triflate and CsF gave xanthenes and xanthones. When the reaction was carried out under basic conditions, 9-hydroxyxanthenes (xanthols) were obtained in good yields.
- Okuma, Kentaro,Nojima, Akiko,Matsunaga, Nahoko,Shioji, Kosei
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supporting information; experimental part
p. 169 - 171
(2009/06/20)
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- A rational approach towards the nucleophilic substitutions of alcohols "on water"
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(Chemical Equation Presented) Walking on water: Which alcohols react with nucleophiles on the surface of water? The correlations introduced by Mayr et al., in which electrophiles are characterized by the parameter E, gives practical indications about the reactivity of alcohols with nucleophiles in pure water. Stable carbocations generated from the alcohols and characterized by E -2.5 readily react with nucleophiles in pure water at 80°C, without added Bronsted or Lewis acids.
- Cozzi, Pier Giorgio,Zoli, Luca
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supporting information; body text
p. 4162 - 4166
(2009/03/11)
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- Pinacol Formation and Reduction of Aromatic Carbonyls with Magnesium-Methanol at Ambient Temperature
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A simple and inexpensive procedure for the pinacol formation of aromatic aldehydes and reduction of aromatic ketones to the corresponding alcohols with magnesium in dry methanol at ambient temperature is reported. The pinacol formation and reduction are proposed to be proceeding by SET from magnesium.
- Khurana, Jitender M.,Bansal, Geeti,Kukreja, Gagan,Pandey, Ravi R.
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p. 1365 - 1371
(2007/10/03)
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- An old but simple and efficient method to elucidate the oxidation mechanism of NAD(P)H model 1-aryl-1,4-dihydronicotinamides by cations 2-methyl-5-nitroisoquinolium, tropylium, and xanthylium in aqueous solution
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Cations 2-methyl-5-mitroisoquinplinium (IQ+), tropylium (T+), and xanthylium (Xn+) were treated by an NAD(P)H model 1-(p-substituted phenyl)-1.4-dihydronicotinamide series (1) in buffered aqueous solution to give the corresponding reduced products by accepting hydride. Effects of the 4-substituents of 1 on the reaction rates were investigated. Hammett's linear free energy relationship analysis on the three reactions of 1 provides the reaction constants of -0.48, -2.2, and -1.4 with IQ+, T+, and Xn+ as the hydride acceptors, respectively. Comparison of the present reactions with the reaction examples whose mechanisms are well-known, such as the reaction of 1 with a one-electron oxidant Fe(CN)6-3, shows that the active site of 1 in the oxidation with IQ+ is at the 4-position on the dihydropyridine ring but that the active site of 1 in the oxidations with T+ and Xn+ is at the 1-position, which is in agreement with the results from the Bronsted-type linear analysis and the relation studies of the logarithm of the second-order rate constants with the oxidation potentials of the hydride donors. According to the dependence of the reaction mechanism on the active site of 1, a conclusion can be made that the reaction of 1 with IQ+ proceeds by direct one-step hydride transfer mechanism, but the reactions of 1 with T+ and Xn+ would take place via multistep hydride transfer mechanism initiated by one-electron transfer.
- Zhu,Liu,Zhao,Cheng
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p. 370 - 375
(2007/10/03)
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- Rapid reduction of carbonyls with nickel boride at ambient utemperature
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Carbonyl compounds have been reported to undergo rapid reduction with nickel boride generated in situ from anhyd. nickel chloride and sodium borohydride in THF at ambient temperature to the corresponding alcohols in high yields.
- Khurana,Chauhan
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p. 3485 - 3489
(2007/10/03)
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- The radical chemistry of t-butyl hydroperoxide (TBHP) - Part 3 - Further studies on hydrocarbon activation
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Further aspects of the chemistry of TBHP in the presence of Fe(II) and Fe(III) species have been investigated. Now all the results previously reported with TBHP can be understood in terms of radical chemistry. Oxidation states of iron higher than Fe(III) are not involved.
- Barton, Derek H. R.,Le Gloahec, Valerie N.
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p. 15457 - 15468
(2007/10/03)
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- Pinacolization and reduction of aromatic carbonyls with aluminium-KOH
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A simple and rapid procedure for the pinacolization of aromatic aldehydes and reduction of hindered ketones with inexpensive aluminium and KOH in methanol at ambient temperature is reported. The pinacolization and reduction are proposed to be proceeding via single electron transfer from aluminium. Copyright 1996 by the Royal Society of Chemistry.
- Khurana, Jitender M.,Sehgal, Arti,Gogia, Amita,Manian, Aparna,Maikap, Golak C.
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p. 2213 - 2215
(2007/10/03)
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- Benzylphosphonic acid inhibitors of human prostatic acid phosphatase
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A series of α-substituted benzylphosphonic acids is described as inhibitors of human prostatic acid phosphatase, an enzyme has been used as a model to study aryl phosphatases. The most potent inhibitors in this series are 2-trifluoromethylbenzhydrylphosphonic acid (9 μM), and α-(2-phenylethyl)benzylphosphonic acid (14 μM). The structure-activity studies suggest that bulk tolerance beyond the phosphate binding area limits the steric or hydrophobic contribution to inhibitor potency achieved through α-carbon substitution.
- Schwender,Beers,Malloy,Cinicola,Wustrow,Demarest,Jordan
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p. 311 - 314
(2007/10/03)
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- THE SELECTIVE FUNCTIONALIZATION OF SATURATED HYDROCARBONS. PART 28. THE ACTIVATION OF BENZYLIC METHYLENE GROUPS UNDER GOAGGIV AND GOAGGV CONDITIONS
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Under GoAggIV and GoAggV conditions, cyclohexadienes were oxidized to give aromatic products instead of ketones and alcohols.At the same time, anthracene was oxidized to give anthraquinone.Under GoAggIV and GoAggV conditions, xanthene, fluorene and diphenylmethane were oxidized to give the corresponding xanthone, fluorenone and benzophenone following two possible pathways: a) alkane to alkyl t-butylperoxide to ketone, and b) alkane to ketone, in which alkyl hydroperoxide, derived from oxygen, may be the reaction intermediate.Xanthyl azide was formed when sodium azide was added to the reaction mixture of xanthene under GoAggIV and GoAggV conditions.The reaction of triphenylmethane under GoAggV conditions gave triphenylmethyl t-butyl peroxide as the major product and hydroperoxide as the minor product.When TEMPO was added, triphenylmethyl hydroperoxide was the only product.
- Barton, Derek H. R.,Wang, Tie-Lin
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p. 1011 - 1032
(2007/10/02)
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- Synthesis and biological activity of 11-[4-(cinnamyl)-1-piperazinyl]-6,11-dihydrodibenz[b,e]oxepin derivatives, potential agents for the treatment of cerebrovascular disorders
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A series of 11-[4-(cinnamyl)-1-piperazinyl]-6,11-dihydrodibenz[b,e]oxepins and related compounds were synthesized and evaluated for their protective activities against complete ischemia, normobaric hypoxia, lipidperoxidation and convulsion. Structure-activity relationship studies of this series led to the finding of (E)-1-(3-fluoro-6,11-dihydrodibenz[b,e]oxepin-11-yl)-4-(3-phenyl-2-prop enyl)piperazine dimaleate (50), AJ-3941 with the most appropriate property for combined pharmacological activities. Compound 50 also shows an inhibitory effect against cerebral edema as well when orally given to rats.
- Kurokawa,Sato,Masuda,Yoshida,Ochi,Zushi,Fujiwara,Naruto,Uno,Matsumoto
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p. 2564 - 2573
(2007/10/02)
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- CIDNP and CIDEP Studies on Intramolecular Hydrogen Abstraction Reaction of Polymethylene-Linked Xanthone and Xanthene. Determination of the Exchange Integral of the Intermediate Biradicals
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Hydrogen abstraction reaction of a polymethylene-linked system is investigated by using chemically induced dynamic nuclear and electron polarization (CIDNP and CIDEP) methods.The reaction scheme is determined from the CIDNP and CIDEP spectra of the unlinked xanthene and xanthone system.The exchange integral J between the two terminal radicals of the system is obtained from the simulation process by using the spin-correlated CIDEP theory modified with (a) the fast population relaxation between the central S-T0 mixed states, (b) the contribution from the triplet mechanism, and (c) hyperfine line dependent line width.The mechanism of the fast population relaxation and the dependence of the J value on the temperature and polymethylene chain length are discussed.
- Maeda, Kiminori,Terazima, Masahide,Azumi, Tohru,Tanimoto, Yoshifumi
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p. 197 - 204
(2007/10/02)
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- Transferts d'electrons assistes par les metaux de transition: influence de la nature du cation metallique sur la reduction de composes carbonyles en milieu aprotique
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The pinacolisation of ketones is enhanced when a bivalent transition metal cation is present.This phenomenon is general and occurs with Cr2+, Mn2+, Fe2+, Co2+, Zn2+ but not with Ni2+.The cathodic reduction leads to α-glycols with a good yield, without any resin production, and at a less negative potential than that of the ketone itself.The distribution of all isolated compounds is dependent on the Lewis character-acidity and complexing power of the metallic cation.Thus, for the dimerization, the greatest specificity is generally observed when Fe2+ is present.For the chalcone, the better stereoselectivity is obtained with Zn2+.No evidence of initial carbonyl complex of the metal ion was shown.
- Fournier, Francoise,Fournier, Michel
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p. 881 - 890
(2007/10/02)
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- Zn/OH- REDUCTIONS OF ORGANIC COMPOUNDS IN DIMETHYLSULFOXIDE ; A NEW SIMPLE METHOD OF PREPARING RADICAL ANIONS
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A new method of preparing radical anions from a variety of organic substrates is proposed that involves the use of Zn/KOH in DMSO as electron source.
- Handoo, Kishan L.,Gadru, Kanchan
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p. 1371 - 1372
(2007/10/02)
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- HETEROCYCLOALKYLATION OF BASES WITH XANTHYLIUM AND THIOXANTHYLIUM SALTS
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Xanthylium and thioxanthylium perchlorates convert tertiary amines into quaternary salts having xanthene and thioxanthene residues at the nitrogen atom.When these reagents are used, the heterocycloalkylation of amines, amides, sulfonamides, imides, and alcohols is not accompanied by disproportionation.
- Ivanov, G. E.,Pavlyuk, G. V.,Turov, A. V.,Ryzhakov, M. K.
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p. 752 - 755
(2007/10/02)
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- HYDRODIMERISATION ELECTROCHIMIQUE DE CETONES AROMATIQUES ENCOMBREES EN MILIEU APROTIQUE ET EN PRESENCE DE CHLORURE DE CHROME
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The electrochemical reduction of hindered aromatic ketones which are difficult to reduce alone, can be achieved in an aprotic medium (DMF) on a mercury pool cathode, in presence of Cr(III) chloride, at the reduction potential of the Cr(II)/Cr(0) system, but at a less negative potential than that of the ketone itself.There is a selective hydrodimerisation into an α-glycol, with total lack of polimerisation.With disymmetric ketones, the dl-diastereoisomers of the diols are produced.The effect of chromium is due either to the reduction of a Cr-ketone complex or to thereduction of the ketone by a film of colloidal chromium on the electrode surface.
- Fournier, F.,Berthelot, J.,Pascal, Y. L.
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p. 339 - 347
(2007/10/02)
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- Ozonation of Xanthene
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The ozonation of xanthene was studied using an oxygen stream.Ozone attacks the methylene group of xanthene via a 1,3-dipolar insertion reaction to give the hydrotrioxide intermediate, followed by a loss of singlet oxygen to form xanthydrol.The ozonation of xanthydrol gave singlet oxygen, water and xanthone accompanied by autoxidation.
- Matsui, Masaki,Miyamoto, Yoshihiko,Shibata, Katsuyoshi,Takase, Yoshimi
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p. 603 - 604
(2007/10/02)
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- Reduction electrochimique de cetones aromatiques encombrees en milieu aprotique et en presence de chlorure de manganese
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The electrochemical reduction of hindered aromatic ketones which are difficult to reduce can be achieved in an aprotic medium (DMF) on a mercury pool cathode, in presence of Mn(II) chloride, at the reduction potential of the Mn(II)?Mn(0) system, but less negative than that of the ketone itself.There is selective hydrodimerization into an α-glycol, with total lack of polymerization.With dissymetric ketones, the dl diastereomers of the diols are produced preferentially.The effect of manganese is due either to the reduction of a Mn(I) or Mn(0) - ketone complex or to the reduction of the ketone by a film of colloidal manganese on the electrode surface.
- Fournier, Francoise,Berthelot, Jacques,Pascal, Yves-Louis
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p. 2121 - 2125
(2007/10/02)
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- Gastric Antisecretory Agents. 2. Antisecretory Activity of 9--9H-xanthenes and 5--5H-benzopyranopyridines
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A series of 9--9H-xanthenes (3-6) and 5--5H-benzopyranopyridines (7-10) possessing gastric antisecretory activity in the rat and dog is described.Many of the compounds possessed good activity in the pylorus-ligated rat and several inhibited histamine-stimulated gastric acid secretion in the dog.The mechanism of acid secretion inhibition is not related to anticholinergic or histamine (H2) receptor antagonism.
- Bristol, James A.,Gold, Elijah H.,Gross, Irwin,Lovey, Raymond G.,Long, James F.
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p. 1010 - 1013
(2007/10/02)
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