- Mechanistic studies on the biomimetic reduction of tetrahydroxynaphthalene, a key intermediate in melanin biosynthesis
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1,3,6,8-Tetrahydroxynaphthalene (T4HN) is an aromatic polyketide, serving as a general precursor of fungal melanin. Melanin biosynthesis involves two consecutive deoxygenations of T4HN, consisting of the reduction of a phenolic carbon followed by dehydrat
- Ichinose,Ebizuka,Sankawa
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p. 192 - 196
(2007/10/03)
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- Radical-mediated cyclisation of ω-aryl-β-dicarbonyl compounds to tetrahydrobenzocyclohepten-6-ones, hexahydrobenzocycloocten-6-ones and naphthalen-2(1H)-ones
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Manganese(III) acetate in acetic acid promotes efficient radical-mediated oxidative cyclisation of ε-aryl-β-dicarbonyl and Z-γ,δ-unsaturated δ-aryl-β-dicarbonyl compounds carrying electron-releasing groups in the aromatic ring, forming 6,7,8,9-tetrahydro-5H-benzocyclohepten-6-ones and naphthalen-2(1H)-ones, respectively. The process is accompanied by secondary acetoxylation at the activated benzylic position of the initial cyclisation products, and is exemplified by the conversions of the ε- and δ-aryl-β-dicarbonyl compounds 6 and 11 into the benzocycloheptenone 18 and the naphthalenone 21, respectively. Application of the oxidation to the formation of 8-membered hexahydro- and tetrahydro-benzocycloocten-6-ones 19 and 22 from ζ-aryl-β-dicarbonyl and Z-γ,δ-unsaturated ζ-aryl-β-dicarbonyl compounds is limited by low reactivity, and in the latter case, by radical rearrangement followed by cyclisation to a tetralin.
- Jamie, Joanne F.,Rickards, Rodney W.
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p. 3613 - 3621
(2007/10/03)
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- DEOXYGENATION IN THE BIOSYNTHESIS OF POLYKETIDES: MECHANISM OF BIOMIMETIC REDUCTION OF TETRAHYDROXYNAPHTHALENE
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A biomimetic synthesis of scytalone, a simple derivative of tetralone, was reinvestigeted using NMR spectroscopy.Scytalone was formed from 1,3,6,8-tetrahydroxynaphthalene (1,3,6,8-THN) by sodium borohydride reduction only in the presence of sodium methoxi
- Ichinose, Koji,Ebizuka, Yutaka,Sankawa, Ushio
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p. 2873 - 2875
(2007/10/02)
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- Depsidone synthesis. Part 24. The synthesis of epiphorellic acid 2. A pseudo-depsidone and x-ray crystal structure of a grisadienedione epoxide
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The synthesis of the unusual pseudo-depsidone epiphorellic acid 2 (2) {6-hydroxy-3-[5-hydroxy-2-methoxycarbonyl-3-(3-oxopentylphenoxy] -4-methoxy-2-pentylbenzoic acid} by a route involving grisadienedione-depsidone rearrangement and subsequent steps is de
- Comber, Mark F.,Sargent, Melvyn V.,Skelton, Brian W.,White, Allan H.
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p. 441 - 448
(2007/10/02)
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- Drugs derived from Cannabinoids. Part 8. The Synthesis of Side-chain Analogues of Δ6a,10a-Tetrahydrocannabinol
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The continuation of studies on the synthesis of side-chain analogues of Δ6a,10a-tetrahydrocannabinol as potential therapeutic agents has led to the syntheses of a possible metabolite 1-hydroxy-6,6,9-trimethyl-7,8,9,10-tetrahydro-6H-dibenzopyran-3-ylacetic acid (1) and 2-(1-hydroxy-6,6,9-trimethyl-7,8,9,10-tetrahydro-6H-dibenzopyran-3-yl)pent-4-ynoic acid (17c).The Pechmann condensation of ethyl 4-methyl-2-oxocyclohexane-1-carboxylate with methyl 3,5-dihydroxyphenylacetate (11), followed by Grignard reaction, was utilized to produce the pyran (1).The key step in the synthesis of the propargylacetic acid (17c) was propargylation of the malonate (15) under phase-transfer catalysis.
- Meltzer, Peter C.,Dalzell, Haldean C.,Razdan, Raj K.
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p. 2825 - 2829
(2007/10/02)
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- Biosynthesis of Fungal Metabolites. Terrein, a Metabolite of Aspergillus terreus Thom
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Terrein, a metabolite of Aspergillus terreus Thom, is biosynthesised from 3,4-dihydro-6,8-dihydroxy-3-methylisocoumarin by contraction of an aryl ring.The direction of the ring contraction has been investigated using acetate as precursor.
- Hill, Robert A.,Carter, Rachel H.,Staunton, James
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p. 2570 - 2576
(2007/10/02)
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- Direct One-Step Conversion of Alcohols into Nitriles
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Alcohols are converted into nitriles in good to excellent yields by treatment with 2 equiv of NaCN/Me3SiCl and a catalytic amount of NaI in DMF/CH3CN.
- Davis, Roman,Untch, Karl G.
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p. 2985 - 2987
(2007/10/02)
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