- ANTHRAQUINONES IN VENTILAGO SPECIES
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Eleven anthraquinones have been isolated from the root bark of Ventilago calyculata of which xanthorin-5-methyl ether and 2-hydroxyislandicin are new natural products.Eight anthraquinones have been isolated from the root bark of V. maderaspatana.Key Word Index - Ventilago calyculata; Ventilago maderaspatana; Rhamnaceae; anthraquinones.
- Rao, B. Kesava,Hanumaiah, T.,Rao, C. P.,Rao, G. S. R.,Rao, K. V. J.,Thomson, Ronald H.
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- Synthetic Studies of the Rubellin Natural Products: Development of a Stereoselective Strategy and Total Synthesis of (+)-Rubellin C
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This manuscript describes our studies of the class of natural products known as the rubellins, culminating in the total synthesis of (+)-rubellin C. These anthraquinone-based natural products contain a variety of stereochemical and architectural motifs, including a 6-5-6-fused ring system, 5 stereogenic centers, and a central quaternary center. Herein, we report our development of a strategy to target the stereochemically dense core and anthraquinone nucleus, including approaches such as a bifunctional allylboron and vinyl triflate reagent, an anthraquinone benzylic metalation strategy, and a late-stage anthraquinone introduction strategy. Our studies culminate in a successful route to highly functionalized anthraquinone-based natural product scaffolds and a stereoselective total synthesis of (+)-rubellin C. These strategies and outcomes will aid in synthetic planning toward anthraquinone-based natural products of high interest.
- Gartman, Jackson A.,Tambar, Uttam K.
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p. 11237 - 11262
(2021/08/16)
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- Synthesis of highly functionalized anthraquinones and evaluation of their antitumor activity
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Highly functionalized anthraquinones which derive from the natural products mensacarcin, islandicin, and chrysophanol have been efficiently synthesized using a Diels-Alder reaction as key step. The introduction of the proposed pharmacophoric side chain unit has been achieved by an addition of an aryllithium species onto different aldehydes. Furthermore, the antitumor activity of these novel compounds has been studied by the in vitro growth inhibition of human lung carcinoma cells of line A549. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Tietze, Lutz F.,Gericke, Kersten M.,Schuberth, Ingrid
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p. 4563 - 4577
(2008/02/12)
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- A VERSATILE SYNTHESIS OF HYDROXY-9,10-ANTHRAQUINONE-2-CARBOXYLIC ACIDS
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Islandicin, a mould metabolite, can be synthesised in a few, robust, high yielding steps.This procedure can be further elaborated to give a variety of hydroxy-9,10-anthraquinone-2-carboxylic acids.
- Smith, Colin W.,Ambler, Samantha J.,Steggles, David J.
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p. 7447 - 7450
(2007/10/02)
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- Biosynthetic Studies on Tajixanthone and Shamixanthone, Polyketide Hemiterpenoid Metabolites of Aspergillus variecolor
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The biosynthesis of tajixanthone and related metabolites of Aspergillus variecolor has been studied by incorporation experiments with simple and advanced precursors labelled with the stable isotopes 13C, 2H and 18O.Tajixanthone is shown to be derived through ring cleavage of an octaketide-derived anthraquinone with introduction of two dimethylallyl moieties.From the results of isotopic labelling experiments and chemical studies on model compounds, an overall biosynthetic pathway is proposed and information on the mechanisms of interconversion of proposed intermediates is obtained.
- Ahmed, Salman A.,Bardshiri, Esfandiar,McIntyre, C. Rupert,Simpson, Thomas J.
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p. 249 - 274
(2007/10/02)
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- A New Synthesis of Anthraquinones Using Dihydro-oxazoles and Grignard Reagents Derived from Mg(Anthracene)(THF)3
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A general synthesis of anthraquinones which depends on the displacement of the methoxy group from an o-methoxyaryldihydro-oxazole by a methoxy substituted benzylmagnesium chloride, generated by using a magnesium-anthracene complex, has been developed.The masked benzylbenzoic acids which result from these reactions are deprotected and then ring-closed to anthrones which on oxidation yield anthraquinones.In this way, the followeing naturally occurring anthraquinones (or derivatives thereof have been synthesized): chrysophanol (9), islandicin (19), digitopurpone (21), tri-O-methylemodin (26), and di-O-methylsoranjidiol (29).
- Nicoletti, Teresa M.,Raston, Colin L.,Sargent, Melvyn V.
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p. 133 - 138
(2007/10/02)
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- A New Synthesis of Anthraquinones
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Methoxy substituted benzyl magnesium chlorides formed by the use of a magnesium anthracene complex smoothly displace the ortho-methoxy group from (o-methoxyaryl)dihydro-oxazoles (oxazolines); the resultant masked o-benzylbenzoic acids are easily converted into anthraquinones.
- Nicoletti, Teresa M.,Raston, Colin L.,Sargent, Melvyn V.
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p. 1491 - 1493
(2007/10/02)
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- A Convenient Synthesis of Isotopically Labelled Anthraquinones, Chrysophanol, Islandicin, and Emodin. Incorporation of Chrysophanol into Tajixanthone in Aspergillus variecolor
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Cycloaddition reactions of labelled 6-methoxy-3-methyl-2-pyrone (1) with naphthoquinones provide the common fungal anthraquinones, chrysophanol (2), islandicin (3), and emodin (4) suitably labelled for biosynthetic studies, as demonstrated by synthesis and incorporation of chrysophanol into the xanthone metabolite, tajixanthone (17) in Aspergillus variecolor.
- Ahmed, Salman A.,Bardshiri, Esfandiar,Simpson, Thomas J.
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p. 883 - 884
(2007/10/02)
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- REGIOSELECTIVE REACTIONS OF 9-HYDROXY-10-CHLORO-1,4-ANTHRAQUINONE. SYNTHESIS OF DIGITOPURPONE AND ISLANDICIN
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9-Hydroxy-10-chloro-1,4-anthraquinone, obtained in the reaction of 1,4-dihydroxy-9,10-anthraquinone with thionyl chloride, is nitrated selectively at the peri position to the chlorine atom and is converted into 5-nitro-9-hydroxy-10-chloro-1,4-anthraquinone.The isomeric 8-nitro-9-hydroxy-10-chloro-1,4-anthraquinone is formed during the hydrolysis of the nitration product and the subsequent reaction of 5-nitro-1,4-dihydroxy-9,10-anthraquinone with thionyl chloride.The reaction of 9-hydroxy-10-chloro-1,4-anthraquinone and its nitro derivatives with the carbanion generated from malonic ester leads to selective alkylation at position 3.Together, the indicated reactions make it possible to realize the regioselective synthesis of 2-methyl-1,4,8- and 2-methyl-1,4,5-trihydroxy-9,10-anthraquinones.
- Gorelik, M. V.,Arinich, L. V.,Kotlyarevskii, O. I.,Fes'kova, E. A.
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p. 129 - 138
(2007/10/02)
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- New Reagents for the Regiospecific Synthesis of Naturally Occurring Quinizarins
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A modified Nef reaction applied to 4-nitrobutanoates gives the corresponding acetals which after hydrolysis and enol silylation yield the new 1,3-dienes 1-methoxy-1,4-bis(trimethylsiloxy)butadiene and its 3-methyl derivative.The latter reacts smoothly with chloronaphthoquinones and provides simple and efficient syntheses of 2-methylquinizarin, islandicin, digitopurpone, and erythroglaucin.
- Simoneau, Bruno,Savard, Jacques,Brassard, Paul
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p. 5433 - 5434
(2007/10/02)
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- The Regiospecific Preparation of 1,4-Dioxygenated Anthraquinones: A New Route to Islandicin, Digitopurpone, and Madeirin
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A direct, versatile, one-step synthesis of anthraquinones which exhibits total regioselectivity (>99 percent) and involves the reaction of the anion of 4- or 7-methoxy-3-phenylsulphonylphthalides with variously substituted quinone monoacetals is reported.
- Russell, Richard A.,Warrener, Ronald N.
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p. 108 - 110
(2007/10/02)
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- Substitution of Quinizarin and 5-Hydroxyquinizarin at C-2
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Carbanions derived from ethyl acetoacetate, acetylacetone, and alkyl nitro-compounds add to C-2 of quinizarin and its 5-hydroxy-derivative.
- Sutherland, James K.,Towers, Patrick,Greenhalgh, Colin W.
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p. 740 - 741
(2007/10/02)
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- Synthetic Anthracyclinones, XIII. Regioselective Synthesis of Digitopurpone and Islandicin by a Combined Diels-Alder and Marschalk Reaction
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The 1,4-ethanoanthraquinone 5b was obtained by regioselective Diels-Alder reaction of the diene 2 with naphthazarin monoethyl ether (1b) followed by hydroxymethylation of the adduct 3b.Clevage of the ether, retrodiene reaction, and reduction gave digitopurpone (7e).Islandicin (8e) was prepared by a similar sequence starting from 4.Both natural products were free of isomers.
- Tolkiehn, Klaus,Krohn, Karsten
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p. 1575 - 1583
(2007/10/02)
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