Showing papers on "Quinone published in 1992"

Oxidation of phenolic arylglycerol .beta.-aryl ether lignin model compounds by manganese peroxidase from Phanerochaete chrysosporium: oxidative cleavage of an .alpha.-carbonyl model compound

Abstract: Manganese peroxidase (MnP) oxidized 1-(3,5-dimethoxy-4-hydroxyphenyl)-2-(4-(hydroxymethyl)-2-methoxyphenoxy) -1,3-dihydroxypropane (I) in the presence of MnII and H2O2 to yield 1-(3,5-dimethoxy-4-hydroxyphenyl)- 2-(4-(hydroxymethyl)-2-methoxyphenoxy)-1-oxo-3-hydroxypropane (II), 2,6-dimethoxy-1,4-benzoquinone (III), 2,6-dimethoxy-1,4-dihydroxybenzene (IV), 2-(4-(hydroxymethyl)-2-methoxyphenoxy)-3-hydroxypropanal (V), syringaldehyde (VI), vanillyl alcohol (VII), and vanillin (VIII). MnP oxidized II to yield 2,6-dimethoxy-1,4-benzoquinone (III), 2,6-dimethoxy-1,4-dihydroxybenzene (IV), vanillyl alcohol (VII), vanillin (VIII), syringic acid (IX), and 2-(4-(hydroxymethyl)-2-methoxyphenoxy)-3-hydroxypropanoic acid (X). A chemically prepared MnIII-malonate complex catalyzed the same reactions. Oxidation of I and II in H2(18)O under argon resulted in incorporation of one atom of 18O into the quinone III and into the hydroquinone IV. Incorporation of one atom of oxygen from H2(18)O into syringic acid (IX) and the phenoxypropanoic acid X was also observed in the oxidation of II. These results are explained by mechanisms involving the initial one-electron oxidation of I or II by enzyme-generated MnIII to produce a phenoxy radical. This intermediate is further oxidized by MnIII to a cyclohexadienyl cation. Loss of a proton, followed by rearrangement of the quinone methide intermediate, yields the C alpha-oxo dimer II as the major product from substrate I. Alternatively, cyclohexadienyl cations are attacked by water. Subsequent alkyl-phenyl cleavage yields the hydroquinone IV and the phenoxypropanal V from I, and IV and the phenoxypropanoic acid X from II, respectively. The initial phenoxy radical also can undergo C alpha-C beta bond cleavage, yielding syringaldehyde (VI) and a C6-C2-ether radical from I and syringic acid (IX) and the same C6-C2-ether radical from II. The C6-C2-ether radical is scavenged by O2 or further oxidized by MnIII, subsequently leading to release of vanillyl alcohol (VII). VII and IV are oxidized to vanillin (VIII) and the quinone III, respectively.

Syntheses and NMR behavior of calix[4]quinone and calix[4]hydroquinone

Abstract: Calix[4]quinone (7) and calix[4]hydroquinone (6) have been synthesized using three different synthetic pathways, The first pathway to 7 from calix[4]arene (1) consists of six steps: acetylation, Fries rearrangement, Baeyer-Villiger oxidation after acetylation, hydrolysis, and oxidation. The second pathway to 7 from 1 consists of four steps: acetylation, Fries rearrangement, reaction of the product obtained by Fries rearrangement with sodium azide, and oxidation.The NMR behavior of 6 and 7 is described

Tyrosinase Reaction/Chitosan Adsorption for Removing Phenols from Wastewater

Abstract: A two-step approach for removing phenols from aqueous solutions was investigated. In the first step, weakly adsorbable phenols are converted to quinones by the enzyme mushroom tyrosinase. The tyrosinase-generated quinones are then chemisorbed onto chitosan, a readily available waste product of the shellfish industry. In the absence of enzyme, quinone was observed to be rapidly adsorbed onto chitosan. Also, the enthalpy for quinone adsorption onto chitosan was observed to be −24.7 kcal/mol, which compares to enthalpies of -7 kcal/mol for adsorption of phenols and quinone onto activated charcoal. With the monophenol reactant cresol, the tyrosinase enzyme was observed to be somewhat stabilized in the presence of chitosan. This stabilization of tyrosinase is presumably due to the rapid adsorption of the reactive quinones onto chitosan. In contrast, tyrosinase was not stabilized by chitosan when the o-diphenol catechol was the reactant. The ability of chitosan to stabilize tyrosinase for monophenols but not for o-diphenols is discussed in terms of the relative rates of phenol oxidation by tyrosinase and quinone chemisorption onto chitosan. When mushroom tyrosinase and chitosan were added simultaneously to dilute, phenol-containing solutions, a nearly complete removal of UV-absorbing material was observed. This observation demonstrates the feasibility of removing phenols from dilute solutions using the tyrosinase reaction/chitosan adsorption approach.

Anthracene-9,10-diones as potential anticancer agents. Synthesis, DNA-binding, and biological studies on a series of 2,6-disubstituted derivatives

Abstract: A series of 2,6-bis(omega-aminoalkanamido)anthracene-9,10-diones (9,10-anthraquinones), of general formula Ar(NHCO(CH2)nNR2)2, where Ar = anthracene-9,10-dione and n = 1 or 2, have been synthesized by treatment of the corresponding bis(omega-haloalkanamido) derivatives with appropriate secondary amines. The DNA-binding properties of these compounds were evaluated by thermal denaturation studies, unwinding of closed-circular DNA, determination of association constants in solution, and examined by molecular modeling. A representative compound in the series has been examined by X-ray crystallography. In vitro cytotoxicity data is reported for the compounds and some indications of structure-activity relationships have been discerned. In particular, those compounds with two methylene links (n = 2) in each side chain separating the amide and terminal amine moieties have superior activity and, in general, enhanced DNA binding characteristics. It is postulated that the mode of reversible binding of these compounds to DNA involves the side chains occupying both major and minor grooves and, further, that this may confer cytotoxic properties which are distinct from those of previously reported anthracene-9,10-dione cytotoxins.

Positive photoresists containing quinone diazide photosensitizer, alkali-soluble resin and tetra(hydroxyphenyl) alkane additive

Abstract: Positive photoresist compositions comprising, in an organic solvent, at least a) one alkali-soluble resin, b) one photosensitive quinone diazide, c) one aromatic hydroxy compound of formula I ##STR1## wherein each R is --H, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, --OCH 2 C 6 H 5 , --OC 6 H 5 or --COOC 1 -C 4 alkyl, and R 1 and R 2 are each independently of the other H, C 1 -C 4 alkyl, --C 6 H 5 or a cycloaliphatic 5- or 6-membered ring, a is an integer from 0 to 4, and m and n are each independently of the other 0, 1 or 2, which compound enhances the photosensitivity and/or the rate of development, and optionally d) additional customary modifiers, are eminently suitable for making relief structures.

Oxidation of vitamin E during iron-catalyzed lipid peroxidation: evidence for electron-transfer reactions of the tocopheroxyl radical.

Abstract: Incubation of phosphatidylcholine liposomes containing the biological antioxidant alpha-tocopherol (alpha-TH) with xanthine, xanthine oxidase, and FeCl2 caused alpha-TH oxidation to alpha-tocopherol quinone (alpha-TQ) and 8a-hydroperoxytocopherone (2). In addition, 4a,5-epoxy-8a-hydroperoxytocopherone (3), 7,8-epoxy-8a-hydroperoxytocopherone (4), and their respective hydrolysis products 2,3-epoxy-alpha-tocopherol quinone (6) and 5,6-epoxy-alpha-tocopherol quinone (7) also were formed. alpha-TQ was the major product at less than 20% alpha-TH oxidation, whereas epoxides were the predominant products when alpha-TH was more extensively oxidized. 8a-(Alkyldioxy)tocopherones 1, which are formed when peroxyl radicals oxidize alpha-TH in other systems and which are precursors to alpha-TQ, were not found. 8a-Hydroxytocopherone (5), rather than 8a-(alkyldioxy)tocopherones 1, appeared to be the precursor to alpha-TQ. Approximately 30% of the alpha-TH consumed was regenerated by treatment of samples with ascorbic acid or nordehydroguaiaretic acid (NDGA) at pH 3, but not at pH 7. The stability of the ascorbic acid- and NDGA-reducible species and pH dependence for regeneration matched those of 8a-hydroxytocopherone (5) and contrasted with the properties of the tocopheroxyl radical (alpha-T.). Incubation of liposomes containing alpha-TH with the diphenylpicrylhydrazyl (DPPH) radical, which oxidizes alpha-TH to alpha-T. in high yield, formed an ascorbic acid-reducible species with properties identical to those of compound 5. The results indicate that phospholipid peroxyl radicals oxidize alpha-T. to epoxides, 8a-hydroperoxytocopherone (2), and the tocopherone cation (alpha-T+), which hydrolyzes to 5, the immediate precursor to alpha-TQ.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxidation of phenolic and non-phenolic substrates by the lignin peroxidase of Streptomyces viridosporus T7A

Abstract: Numerous single-ring, aromatic, phenolic and non-phenolic compounds were tested as substrates of Streptomyces viridosporus T7A extracellular lignin peroxidase. Oxidations were monitored by spectroscopy, with and without 4-aminoantipyrine (4-AAP) as a color-forming reagent. The oxidation of phenols containing one or no carbon groups in the para position resulted in coupling with 4-AAP to form a red color. Thin layer chromatography and mass spectroscopy showed that the oxidation of vanillic acid (4-hydroxy-3-methoxybenzoic acid) and syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid) resulted in a direct coupling between 4-AAP and the phenol ring to form a quinone structure. In the reaction with vanillyl acetone (4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-one) and 4-AAP, 4-AAP coupled to A-carbon of vanillyl acetone. As shown by UV-visible spectroscopy, S. viridosporus T7A peroxidase oxidized phenolic compounds, but was unable to oxidize non-phenolic ones.

Inhibition of NAD(P)H:(quinone-acceptor) oxidoreductase by cibacron blue and related anthraquinone dyes: a structure-activity study.

Abstract: Cibacron Blue, a widely used ligand for affinity chromatography, is a potent inhibitor of NAD(P)H:(quinone-acceptor) oxidoreductase (EC 1.6.99.2) (quinone reductase). This property has been exploited to purify quinone reductase, to identify its nucleotide-binding site, and to obtain diffraction-grade crystals of this enzyme [Prochaska, H. J. (1988) Arch. Biochem. Biophys. 267, 529-538; Ysern, X., & Prochaska, H. J. (1989) J. Biol. Chem. 264, 7765-7767]. To define the structural region(s) of the dye responsible for its inhibitory potency, Cibacron Blue was synthesized and the dye, its synthetic intermediates, and some analogues of these intermediates were crystallized as novel trialkylamine or choline salts. These compounds were characterized by proton NMR and mass spectrometry, and their inhibitory potencies were measured. Only two of the four ring systems of the Cibacron Blue molecule are required for potent inhibition. Acid Blue 25 [1-amino-4-(phenylamino)anthraquinone-2-sulfonic acid] is an inhibitor (Ki = 22 nM) almost as potent as Cibacron Blue (Ki = 6.2 nM). However, removal of any of the three substituents on the anthraquinone ring of Acid Blue 25 markedly reduced inhibitory potency. These results are consistent with the proposal that Cibacron Blue is primarily a mimic for the ADP fragment of mono- and dinucleotides. The difference absorption spectrum of the Acid Blue 25-quinone reductase complex was very different from that of the complex with Cibacron Blue. In contrast to other compounds tested, Procion Blue M-3GS, the electrophilic dichlorotriazine precursor of Cibacron Blue, was an irreversible inhibitor of quinone reductase (KD = 16 nM, k3 = 0.03 min-1), and the inactivation was blocked by Cibacron Blue, a monochlorotriazine.

Hydroperoxidation of alkanes by atmospheric oxygen in the presence of hydroquinone or quinone catalyzed by copper(II) acetate under visible light irradiation

Abstract: When a solution of an alkane and hydroquinone (or quinone) in CH3CN irradiated in air by visible light in the presence of catalytic amounts of Cu(OCOCH3)2, the alkyl hydroperoxide is formed.

Mixed-valence, conjugated quinone and imide anion radicals. An ESR investigation

Abstract: Anion radicals of linear polyacene diquinones and diimides were produced electrochemically and studied by ESR. The odd electron of substituted 1,4,8,11-pentacenetrone anion radicals is localized (in a naphthoquinoid unit) and hops from one quinone to the other. The hopping rate was measured. The anion radicals of similarly sized anthracenetetracarboxylic acid 2,3:6,7-diimides have a delocalized odd electron, and there is relatively high electron density on the bridge. The results are compared to other unconjugated two-electrophore anion radicals

Redox-active crown ethers. Electrochemical and electron paramagnetic resonance studies on alkali metal complexes of quinone crown ethers

Abstract: Structural studies on [M(NCS)-(SQC-HQDME)] (M=Li, Na) as well as free (QC-HQDME and [M(NCS)((QC-HQDME)] (M=Na, K) (where SQC-HQDME is 15,17-dimethyl-1(,18-dimethoxy-3,6,9,12-tetraoxabicyclo[12.3.1]octadeca(1,14,16)triene, and (QC-HQDME is 15,17-dimethyl-16,18-dimethoxy-3,6,9,12,15-pentaoxabicyclo[15.3.1]heneico (1,14,1()triene) show that in all cases the metal ion binds to the anisole oxygen atom in the 1-position.

Intramolecular photochemical electron transfer. 7. Temperature dependence of electron-transfer rates in covalently linked porphyrin-amide-quinone molecules

Abstract: Intramolecular rate constants WET for electron transfer (ET) from a porphyrin excited singlet S 1 state to a linked quinone acceptor have been measured as a function of temperature in several solvents for the molecule PAQ [5,10,15-tritolyl-15-(4-carboxylphenyl)porphine linked to p-benzoquinone via an amide group]. Most of the data could be analyzed sucessfully using the high-temperature form of the semiclassical Marcus equation. The analysis of temperature dependence data allows the separation of the electronic and nuclear factors in the Marcus equation

Quinone photochemistry. A general synthesis of acylhydroquinones

Abstract: The synthesis of dihydroxy ketones such as 1 is usually accomplished by a sequence involving Friedel-Crafts acylation and hydrolysis.’ Disciplines Chemistry | Environmental Chemistry | Inorganic Chemistry | Organic Chemistry | Other Chemistry | Polymer Chemistry Comments Reprinted (adapted) with permission from The Journal of Organic Chemistry, 57(11); 3256-3257. Doi: 10.1021/jo00037a058. Copyright 1992 American Chemical Society. This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/chem_pubs/619 3256 J. Org. Chem. 1992,57,3256-3257 to give a continuous stream emanating from the condenser tip (for heat insulation the pressure-equalizing side arm of the addition funnel was wrapped with several layers of paper towel). The Teflon stopcock on the addition funnel was opened only slightly 80 as to minimize the entry of the hexane vapors from this inlet and yet fully drain all eluted solvent into the still-pot. Once started, the system was allowed to continue until all of the purple Cso had collected in the still-pot (20-30 h). The still-pot was then removed and the solvent evaporated6 to afford ca. 170 mg of pure (HPLC, W-vis) Cso which was separated from the boiling chips by dissolution in CS2 followed by suction filtration and precipitation from the filtrate with pentane. A new 2OOO-mL two-neck round-bottom flask containing 1.5 L of hexane was then installed and the above process repeated to elute pure C,o from the column (70 h). The solvent was evaporated, and 30 mg of pure (HPLC, UV-vis) CT0 was isolated. So far we have performed about 15 of these separations, all with high reproducibility. We believe the reason for the success of the separation lies not only in the use of lowest polarity solvents but also in the elevated temperaturelo due to the Soxhlet extraction process. It is possible that our results would not have been nearly as good had we tried the related apparatus of ref 6. Acknowledgment. We thank the National Science Foundation for support through Grants DMR-88-20933, DMR-91-11097, and CHE89-08323. We also thank Miklos Csuja for the glassware modifications. alumina, 1344-28-1. Registry NO. Cm, 9968596-8; C,or115383-22-7; C, 7440-44-0; (10) Pirkle and Welch (Pirkle, W. H.; Welch, C. J. J. Org. Chem. 1991, 56,6973) have found that better separations of CW/C,~ occur at higher temperature. Quinone Photochemistry. A General Synthesis of Acylhydroquinones George A. Kraus* and Masayuki Kirihara Department of Chemistry, Iowa State University, Ames, Iowa 50011 Received September 30, 1991 The synthesis of dihydroxy ketones such as 1 is usually accomplished by a sequence involving Friedel-Crafts acylation and hydrolysis.’ This sequence works well in

Role of quinone-iron(III) interaction in NADPH-dependent enzymatic generation of hydroxyl radicals.

Abstract: To study the effect of chelation of iron ions by quinones on the generation of OH radicals in biological redox systems, we have synthesized quinones that can form complexes with Fe(III) ions: 2-phenyl-4-(butylamino)naphtho[2,3-h]quinoline-7,12-dione (Qbc) and 2-phenyl-4-(octylamino)naphtho[2,3-h]quinoline-7,12-dione (Qoc). A quinone with a similar structure without chelating group was synthesized as a control sample: 2-phenyl-5-nitronaphtho[2,3-g]indole-6,11-dione (Qn). Using optical spectroscopy, we determined the stability constant of Qbc with Fe(III) [Ks = (7 +/- 1) x 10(18) M-3] and the stoichiometry of the complex Fe(Qbc)3 in chloroform solutions. One-electron reduction potentials of Qbc, Qn, and adriamycin in dimethyl sulfoxide were measured by cyclic voltammetry. In the presence of Fe(III) the one-electron reduction potentials shifted toward positive values by 0.16 and 0.1 V for Qbc and adriamycin, respectively. Using the spin trap 5,5'-dimethyl-1-pyroline N-oxide (DMPO) and EPR, it was found that Qbc in the Fe(III) complex stimulated the formation of OH radicals in the enzymatic system consisting of NADPH and NADPH-cytochrome P-450 reductase more efficiently than adriamycin and quinone Qn. This is indicated by the absence of a lag period in the spin adduct appearance for Qbc and by a significantly higher rate of the spin adduct production, as well as by a larger absolute concentration of the spin adduct obtained for Qbc in comparison with Qn in the presence of Fe(III).(ABSTRACT TRUNCATED AT 250 WORDS)

Carbonyl O‐Oxides and Dioxiranes: The Influence of Substituents on Spectroscopic Properties

Abstract: Triplet 4-oxocyclohexadienylidenes 6, matrix-isolated in Ar/ 2% O2 at 10 K, react with triplet O2 on annealing the matrix. Primary reaction products are quinone oxides 4, which have been characterized by IR and UV/Vis spectrometry. They are very photolabile; long-wavelength irradiation converts them into spiro-dioxiranes 5, which in turn yield lactones 10 upon irradiation with visible light. Experimental data have been obtained for quinone oxides 4a–g; additionally, ground-state properties and UV/Vis absorptions of quinone oxides 4a,b and 4e–1 have been calculated by the MINDO-3/UHF and CNDO/S methods. Since the theoretical and experimental maxima of the π π* transitions are in good agreement, we conclude that our semiempirical calculations give an adequate picture of quinone oxides 4 which may best be described as dipolar diradicals.

Synthesis of Optically Active p-Tolylsulfinylquinones

Abstract: The title compounds 3 a-e were prepared in only two steps from 1,4-dimethoxyaromatic precursors 1a-e by sulfinylation followed by oxidation with ammonium cerium(IV) nitrate