- Inhibition of Urease, a Ni-Enzyme: The Reactivity of a Key Thiol With Mono- and Di-Substituted Catechols Elucidated by Kinetic, Structural, and Theoretical Studies
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The inhibition of urease from Sporosarcina pasteurii (SPU) and Canavalia ensiformis (jack bean, JBU) by a class of six aromatic poly-hydroxylated molecules, namely mono- and dimethyl-substituted catechols, was investigated on the basis of the inhibitory efficiency of the catechol scaffold. The aim was to probe the key step of a mechanism proposed for the inhibition of SPU by catechol, namely the sulfanyl radical attack on the aromatic ring, as well as to obtain critical information on the effect of substituents of the catechol aromatic ring on the inhibition efficacy of its derivatives. The crystal structures of all six SPU-inhibitors complexes, determined at high resolution, as well as kinetic data obtained on JBU and theoretical studies of the reaction mechanism using quantum mechanical calculations, revealed the occurrence of an irreversible inactivation of urease by means of a radical-based autocatalytic multistep mechanism, and indicate that, among all tested catechols, the mono-substituted 3-methyl-catechol is the most efficient inhibitor for urease.
- Mazzei, Luca,Contaldo, Umberto,Musiani, Francesco,Cianci, Michele,Bagnolini, Greta,Roberti, Marinella,Ciurli, Stefano
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supporting information
p. 6029 - 6035
(2021/02/09)
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- Synthesis of methylated quercetin analogues for enhancement of radical-scavenging activity
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Three quercetin derivatives with enhanced radical-scavenging activity were designed and synthesised. Because the radical-scavenging reaction of quercetin is known to proceed via an electron transfer from quercetin to radicals, producing the corresponding quercetin radical cation intermediate, the introduction of electron-donating groups into the quercetin molecule is expected to enhance its radical-scavenging activity. Thus, methyl groups were introduced into the catechol moiety in the quercetin molecule at either the 2′- or 5′-position, or both. All three quercetin analogues were found to exhibit higher radical-scavenging activity than the parent quercetin. The activity of 5′-methylquercetin is the highest among the three analogues. The optimised structure of 5′-methylquercetin calculated by density functional theory demonstrated a coplanar structure between the 4H-curomen (AC rings) and catechol (B ring) moieties, while dimethylquercetin and 2′-methylquercetin have a twisted structure between the AC and B rings. These results demonstrate that the highest radical-scavenging activity of 5′-methylquercetin is due to the stabilisation of the radical cation intermediate by the electron-donating effect of the methyl group as well as by the planar structure of the molecule.
- Imai, Kohei,Nakanishi, Ikuo,Ohkubo, Kei,Ohba, Yusuke,Arai, Takuya,Mizuno, Mirei,Fukuzumi, Shunichi,Matsumoto, Ken-ichiro,Fukuhara, Kiyoshi
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p. 17968 - 17979
(2017/03/31)
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- Catalytic activity of Fe-porphyrins grafted on multiwalled carbon nanotubes in the heterogeneous oxidation of sulfides and degradation of phenols in water
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A biomimetic heterogeneous catalyst was prepared by immobilization of meso-tetrakis(4-carboxyphenyl)porphyrinatoiron(III) chloride (Fe(TCPP)Cl) on multiwalled carbon nanotubes (MWCNTs). The anchored catalyst was characterized by transmission electron microscopy, powder X-ray diffraction, ultraviolet–visible, and Fourier transform infrared spectroscopy. The amount of Fe-porphyrin loaded on the nanotubes was estimated by atomic absorption spectroscopy The thermogravimetric analysis demonstrated that the catalyst was thermally stable up to almost 350 °C, exhibiting high thermal stability. Oxidation of sulfides and phenols with urea hydrogen peroxide (UHP) in water was efficiently enhanced with excellent selectivity under the influence of [Fe(TCPP)Cl@MWCNT]. The title heterogeneous catalytic system facilitates a greener reaction because the reaction solvent is water and UHP is used as a safe oxidant.
- Rayati, Saeed,Nejabat, Fatemeh
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p. 967 - 974
(2017/09/26)
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- Synthesis and radical-scavenging activity of a dimethyl catechin analogue
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Catechin analogue 1 with methyl substituents ortho to the catechol hydroxyl groups was synthesized to improve the antioxidant ability of (+)-catechin. The synthetic scheme involved a solid acid catalyzed Friedel-Crafts coupling of a cinnamyl alcohol derivative to 3,5-dibenzyloxyphenol followed by hydroxylation and then cyclization through an intermediate orthoester. The antioxidative radical scavenging activity of 1 against galvinoxyl radical, an oxyl radical, was found to be 28-fold more potent than (+)-catechin.
- Imai, Kohei,Nakanishi, Ikuo,Ohno, Akiko,Kurihara, Masaaki,Miyata, Naoki,Matsumoto, Ken-Ichiro,Nakamura, Asao,Fukuhara, Kiyoshi
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p. 2582 - 2584
(2014/05/20)
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- Asymmetric syntheses of highly functionalized bicyclo [2.2.2] octene derivatives
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Highly functionalized bicyclo[2.2.2]octene derivatives bearing two quaternary carbon centers were synthesized in an asymmetric fashion. The key transformations were the regioselective Diels-Alder reaction between 3,6-dimethyl-o-quinone monoacetal and 1,1-diethoxyethylene and the subsequent enzymatic resolution. The optically active bicyclo[2.2.2]octene derivatives obtained should serve as versatile chiral building blocks for highly functionalized natural products such as ryanodine. The Japan Institute of Heterocyclic Chemistry.
- Iwatsu, Masafumi,Urabe, Daisuke,Inoue, Masayuki
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p. 491 - 504
(2013/08/23)
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- New families of enantiopure cyclohexenone cis-diol, o-quinol dimer and hydrate metabolites from dioxygenase-catalysed dihydroxylation of phenols
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Toluene dioxygenase-catalysed cis-dihydroxylation of phenols has led to the discovery of new enantiopure cyclohexenone cis-diol, o-quinol dimer and phenol hydrate metabolites having synthetic potential.
- Boyd, Derek R.,Sharma, Narain D.,Malone, John F.,Allen, Christopher C.R.
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supporting information; experimental part
p. 3633 - 3635
(2009/12/02)
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- An expedient one-pot entry to catecholestrogens and other catechol compounds via IBX-mediated phenolic oxygenation
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A one-pot procedure for the preparation of catecholestrogens in over 90% yield is reported, involving oxygenation of 17β-estradiol or estrone with o-iodoxybenzoic acid (IBX) followed by reduction with methanolic NaBH 4. The procedure, which was extended to the o-hydroxylation of a number of representative phenols in good-to-high yields, expands significantly the scope of phenolic oxidation mediated by IBX.
- Pezzella, Alessandro,Lista, Liliana,Napolitano, Alessandra,D'Ischia, Marco
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p. 3541 - 3544
(2007/10/03)
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- Heterocyclic amide derivatives
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The present invention relates to novel heterocyclic amide derivatives of the formula in which R1, R2, R3 and R4 are as defined in the disclosure, to a process for preparing them, and to their use as pesticides.
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- Synthesis of cyanodibenzo[1,4]dioxines and their derivatives by cyano-activated fluoro displacement reactions
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A new group of cyanodibenzo[1,4]dioxines have been synthesized by cyano-activated fluoro displacement reactions between cyanodifluorobenzenes and catechols in DMF at 130°C in the presence of potassium carbonate. This route is exemplified by the synthesis of cyanodibenzo[1,4]dioxines from several substituted catechols. The reactions are virtually quantitative. Cyanodibenzo[1,4]dioxines were hydrolysed with potassium hydroxide in ethylene glycol or converted into amide derivatives to yield additional substituted dibenzo[1,4]dioxines. Cyanodibenzo[1,4]-dioxines are fluorescent and excitation and emission data are presented. Improved syntheses of 4,5-diphenyl-veratrole and 3,6-dimethylcatechol, the latter involving reduction of a phenolic Mannich base at atmospheric pressure, have been elaborated.
- Eastmond,Paprotny,Steiner,Swanson
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p. 379 - 384
(2007/10/03)
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- On Dien-Ketenes from o-Quinol-Acetates
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A detailed picture of the photochemistry of o-quinol-acetates is presented. (RS)-6-Acetoxy-6-methyl-, (RS)-6-acetoxy-2,6-dimethyl-, (RS)-6-acetoxy-5,6-dimethyl-, (RS)-6-acetoxy-2,4,6-trimethyl-, (RS)-6-acetoxy-2,3,4,6-tetramethyl-, and (RS)-6-acetoxy-2,3,4,5,6-pentamethyl-2,4-cyclohexadien-1-ones serve as representative educts.There are two separate main photochemical routes conveniently designated as 1(?*,n) or 3(?*,?) tracks.The latter may also be attained by sensitization and leads to phenols.The former, by α-cleavage furnishes dien-ketens as indispensable phototransients.Photolysis of dien-ketens follows one or more of three reaction channels, each of which yields a particular type of photoproduct: heat-induced monocyclization affords 2,4-cyclohexadien-1-ones, heat-induced bicyclization stereoselectively furnishes bicyclohex-3-en-2-ones, and multi-step addition of protic nucleophiles stereoselectively gives 1,4-, 1,6- and/or 1,2-adducts.By X-ray analysis or NOE studies, the structure of isolated photoproducts is established.Conventional spectroscopy at low or flash spectroscopy at normal temperature yield information on the formation and decay of kinetically unstable intermediates.Photoproduct composition depends on the pattern of substitution of the educts, on the solvents, and on the nucleophiles that migth be present.Substituents primarily exert an influence upon the population of the various conformers of the dien-keten.Solvents affect the rate of the divers reaction paths competing for the phototransient.Nucleophiles play more than a trivial role when adducts are formed.With the detailed view of a dien-keten's role on hand, the photoproduct from a given o-quinol-acetate - or more general from a linear conjugated cyclohexadienone - is now predictable.
- Quinkert, Gerhard,Kleiner, Erna,Freitag, Bernd-Juergen,Glenneberg, Juergen,Billhardt, Uta-Maria,et al.
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p. 469 - 537
(2007/10/02)
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- Host-Guest Complexation. 25. Effects of Substituents on the Complexing Properties of Chorands
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The syntheses of three benzannelated 18-crown-6 chorands (3,6,and 7) and three dibenzo-20-crown-6 chorands (10b-d) are reported, along with their free energies of association toward Li+, Na+, K+, Rb+, Cs+, NH4+, CH3NH3+, and t-BuNH3+ picrates in CDCl3 at 25 deg C.For the 18-membered chorands, as well as previously reported paracyclophane-18-crown-6 hosts and naphtho-18-crown-6 hosts, the average negative free energies of association (-ΔG0av)for Li+, Na+, K+, Rb+, Cs+, and NH4+ picrates were qualitatively correlated with the degree of coplanarity of β-aryl substituents and the aromatic rings.The results are interpreted in terms of conformational organization of ligating sites in comparision with organization observed in crystalline complexes.Substuents were found to enhance complexation in the dibenzo-20-crown-6 series.This is interpreted as an effect of ligating-site preorganization and free-host destabilization.Substituent effects in chiral bicyclohexyl (13) and meso-bicyclohexyl hosts (14) are explained in similar terms.
- Bell, Thomas W.,Lein, George M.,Nakamura, Hideo,Cram, Donald J.
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p. 4728 - 4734
(2007/10/02)
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