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Quinones 2-methyl-1,4-naphthoquinone

On the other hand. Biggins examined various benzo-, naphtho- and anthraquinones and found a more stringent structural requirement for areplacement quinone to be functional at the A i site. It was specifically noted that among the many types of quinones, only naphthoquinones possessing a hydrocarbon chain at the 3-position, namely, 2-methyl-3-decyl-, 2-methyl-3-(isoprenyl)2- and 2-methyl-3-(isoprenyl)4-naphthoquinones, similar to phylloquinone with the 3-phytyl chain, could provide the required molecular structure for interaction with the hydrophobic domain at the A site, as confirmed by the criterion of P700 /P430 recombination kinetics. All other quinones presumably could oxidize Aq but the reduced quinone then recombined directly with P700. It was also noted that 2,3-dimethyl-1,4-naphthoquinone,... [Pg.601]

The term vitamin K2 was applied to 2-methyl-3-difarnesyl-l,4-naphthoquinone, m.p. 54 C, isolated from putrefied fish meal. It now includes a group of related natural compounds ( menaquinones ), differing in the number of isoprene units in the side chain and in their degree of unsaturation. These quinones also appear to be involved in the electron transport chain and oxidative phosphorylation. [Pg.423]

Quinones of various degrees of complexity have antibiotic, antimicrobial, and anticancer activities, eg, a2iddinornitosene [80954-63-8] (36), (-)-2-methyl-l,4-naphthoquinone 2,3-epoxide [61840-91 -3] (37), and doxombicin [23214-92-8] (adriamycin) (38) (see Antibiotics Chemotherapeutics, anticancer), ah of these natural and synthetic materials have stimulated extensive research in synthetic chemistry. [Pg.407]

Thallium trinitrate oxidi2es naphthols and hydroquinone monoethers, respectively, to quinones and 4,4-diaIkoxycyclohexa-2,5-dienones, eg, 4,4-dimethoxy-2-methyl-2,5-cyclohexadienone [57197-11 -2] (108) (111,112). The yield of (108) is 89%. Because the monoacetal is easily converted to the quinone, the yield of 5-hydroxy-l,4-naphthoquinone [481-39-0] is 64%. [Pg.417]

The shikimate pathway is the major route in the biosynthesis of ubiquinone, menaquinone, phyloquinone, plastoquinone, and various colored naphthoquinones. The early steps of this process are common with the steps involved in the biosynthesis of phenols, flavonoids, and aromatic amino acids. Shikimic acid is formed in several steps from precursors of carbohydrate metabolism. The key intermediate in quinone biosynthesis via the shikimate pathway is the chorismate. In the case of ubiquinones, the chorismate is converted to para-hydoxybenzoate and then, depending on the organism, the process continues with prenylation, decarboxylation, three hydroxy-lations, and three methylation steps. - ... [Pg.102]

Many quinones (including anthracyclines considered above) are well-known prooxidants that makes them potential DNA damaging agents. It has been shown that menadione (2-methyl-1,4-naphthoquinone), a redox cycling quinone, induced single- and double-strand... [Pg.839]

As hydroxyl or hydroxyl-like radicals are produced by the superoxide-driven Fenton reaction, superoxide overproduction must also occur in thalassemic cells. First, it has been shown by Grinberg et al. [382], who demonstrated that thalassemic erythrocytes produced the enhanced amount of superoxide in comparison with normal cells in the presence of prooxidant antimalarial drug primaquine. Later on, it has been found that the production of superoxide and free radical-mediated damage (measured through the MetHb/Hb ratio) was much higher in thalassemic erythrocytes even in the absence of prooxidants, although quinones (menadione, l,4-naphthoquinone-2-methyl-3-sulfonate) and primaquine further increased oxidative stress [383]. Overproduction of superoxide was also observed in thalassemic leukocytes [384]. [Pg.941]

Further reduction of quinones - acquisition of four or more hydrogens per molecule - was achieved with lithium aluminum hydride which reduced, in yields lower than 10%, 2-methyl-1,4-naphthoquinone to 1,2,3,4-tetrahydro-l,4-dihydroxy-2-methylnaphthalene and to l,2,3,4-tetrahydro-4-hydroxy-l-keto-2-methylnaphthalene [931]. Lithium aluminum hydride [931], sodium borohydride, lithium trie thy Iborohydride and 9-borabicyclo[3.3.1Jnomine [100] converted anthraquinone to 9,10-dihydro-9,10-dihydroxyanthracene in respective yields of 67, 65, 77 and 79%. [Pg.129]

Aromatic compounds are oxidized to quinones by bis(triorganosilyl) peroxides in the presence of a metal acid catalyst. Thus, 2-methylnaphthalene was oxidized with BTSP in the presence of Re207 and BU3PO in the presence of CHCI3, to a mixture of 59% 2-methyl-1,4-naphthoquinone and 8% 6-methy 1-1,4-naphthoquinone. ... [Pg.795]

Menaquinone. The incorporation of [2- C]mevalonate and [2- C]-2-methyl-l,4-naphthoquinone into MK-4, normally considered a bacterial quinone, has been demonstrated in marine invertebrates such as crabs and starfish." Incorporation into 2,3-epoxy-MK-4 (163) was also observed. Cell-free extracts have been prepared from Escherichia coli which catalyse the conversion of o-succinylbenzoic acid (164) into l,4-dihydroxy-2-naphthoic acid (165) and menaquinones. In the presence of farnesyl pyrophosphate the major menaquinone produced was MK-3. Genetic studies with mutants of E. coli K12 that require (164) offer support for the generally accepted pathway for MK biosynthesis via (164) and (165)." The enzyme system that catalyses the attachment of the polyprenyl side-chain to 1,4-dihydroxy-2-naphthoic acid to form demethylmenaquinone-9 (166) has been isolated from E. colU ... [Pg.208]

Molecular electrostatic potentials have been used to explain the regioselectivity exhibited in the Diels-Alder cycloaddition reactions between 1-trimethylsilyloxy-butadiene and the quinones 5-formyl-8-methyl-1,4-naphthoquinone, 5-methoxy-7-methyl-1,4-phenanthrenequinone, and 5,6,7-trimethyl-1,4-phenanthrenequinone.128 The intramolecular Diels-Alder reaction of masked o-benzoquinones (123) with a variety of dienes provides adducts (124) which rearrange to functionalized ris-decal ins (125) with complete stereocontrol of up to five stereocentres. This methodology ... [Pg.372]

Photolysis of 5-methyl-1,4-naphthoquinone (24) gives 4-hydroxy-5-methyli-dene naphthalen-1 (5//)-one (25) in the ground state within 2 ps of excitation, with a quantum yield of 1.0.59 Formally, this is a photoenolization reaction however, the product of the reaction also has quinone methide functionality,... [Pg.51]

Syntheses of a- and p- lapachones and their homologues were carried out by photochemical side chain introduction to quinone. Thus, 1,4-naphthoquinone photochemically reacted with 3-methyl-2-butenal to give 2-(3-methyl-2-butenoyl)-l,4-naphthalenediol (69), regiospecifically. The product (69) was successively treated with acid, with dichloroaluminiun hydride, and finally with iron (III) chloride to derive in turn to cromanon (70), dihydropyran (71), and P-lapachone (35). P-lapachone was easily transformed to a-lapachone (38) by treating with acid. Likewise, from... [Pg.740]

Some synthetic lapachol derivatives have also showed cytotoxic activity. Burton et al have prepared mono(arylimino) derivatives of P-lapachone. Some of these derivatives had good scores with net cell kills in preliminary in vivo testing hollow fiber assays against a standard panel of 12 human tumor cell lines [160].Twelve substituted 1,4-naphthoquinones were tested against the ascitic form of sarcoma 180 in Swiss mice. Statistical analysis showed that the most important molecular parameter determining their effectiveness in prolonging the life of mice bearing this tumor is their redox potentials [161]. Zalkow et al have synthesized a monoimine quinone, namely 2-methyl-(Z)-4-phenylimino)naphth[2,3-d]oxazol-9-one, which in in vitro tests showed a selective activity for some solid cancer tumors [162]. Enamine derivatives of lapachol were... [Pg.744]

Polyprenylation of quinones. Trimethylstannyllithium converts polyprenyl halides (e.g., geranyl chloride, phytyl chloride) into polyprenyltrimethylstannyl compounds in high yield with retention of stereochemistry of the allylic double bond. In the presence of a Lewis acid (BF3 etherate) these tin compounds couple regio- and stereoselectively with 2-methyl-l,4-naphthoquinone. The reaction to form vitamin K (2) is typical (equation I). ... [Pg.556]

Polycyclic quinones are prepared by careful oxidation of the corresponding hydrocarbons with chromic-sulfuric acid mixture in acetic acid solution or as an agitated aqueous suspension, e.g., 2,3-dimethy 1-1,4-naphthoquinone (80%), 9,10-phenanthroquinone (80%), and acenaphthene-quinone (60%). A laboratory reactor has been described in which an acetic acid solution of chromic acid and another solution of hydrocarbon are mixed as a film at 90°. The reaction mixture is then fed into water to prevent ftirther oxidation. By this procedure, the yield of 2-methyl-1,4-naphthoquinone has been raised from 29% by the usual process to... [Pg.204]


See other pages where Quinones 2-methyl-1,4-naphthoquinone is mentioned: [Pg.141]    [Pg.146]    [Pg.102]    [Pg.105]    [Pg.87]    [Pg.155]    [Pg.155]    [Pg.225]    [Pg.57]    [Pg.22]    [Pg.81]    [Pg.205]    [Pg.44]    [Pg.201]    [Pg.781]    [Pg.249]    [Pg.434]    [Pg.249]    [Pg.223]    [Pg.408]    [Pg.409]    [Pg.2151]    [Pg.735]    [Pg.547]    [Pg.155]    [Pg.400]    [Pg.406]    [Pg.231]    [Pg.149]    [Pg.249]    [Pg.54]   
See also in sourсe #XX -- [ Pg.433 ]




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1 : 4-Naphthoquinone

2-Methyl-1,4-Naphthoquinon

Naphthoquinones quinone

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