Biomimetic Synthesis of the Flavanone Leridol, Revision of the Structure of the Natural Product

Solladié, Guy; Gehrold, Nicolai; Maignan, Jean

doi:10.1002/(sici)1099-0690(199909)1999:9<2309::aid-ejoc2309>3.3.co;2-0

Cited by 2 publications

(1 citation statement)

References 5 publications

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“…[6] Kostanecki realized the transformation 1Ǟ2 (Figure 1, a) for the first time in 1904 with a mineral acid catalyst. [7] In the meantime, a wide range of catalytic reagents and conditions have been found to induce the cyclization, including: aqueous buffers at variable pH, [6,8] mineral acids, [7,9] acidic ion-exchange resin, [10] acetic acid, [11] alkali metal hydroxide [6,8b,12] (sometimes combined with phase-transfer catalysts), [13,14] sodium acetate, [8m,15] potassium fluoride, [16] amine bases, [14,17,18] amino acids, [14] photoirradiation, [19] thermal reaction at 60°C in the solid state [20] or in the melt at 230°C, [21] catalysis by Co III -salen complexes, [22] Lewis acids, [11a,23] SiO 2 , [24] or under electrochemical conditions. [25] All of these methods have in common that they give racemic flavanone (2).…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Cyclization of 2′‐Hydroxychalcones to Flavanones: Catalysis by Chiral Brønsted Acids and Bases

2007

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The asymmetric cyclization of 2′‐hydroxychalcones to flavanones is a basic, enzyme‐catalyzed step in the biosynthesis of flavonoid natural products, but poses a long‐standing problem for asymmetric catalysis with small molecule catalysts. Earlier claims concerning the realization of an asymmetric flavanone synthesis by means of camphorsulfonic acid as chiral Brønsted acid catalysts were reinvestigated using accurate HPLC methods for quantification of enantiomer ratios. The previous claims of asymmetric induction were thus shown to be untenable. On the other hand, cinchona alkaloids serve as chiral Brønsted base mediators for the asymmetric cyclization of either 6′‐substituted 2′‐hydroxychalcones or 2′,6′‐dihydroxychalcones. 2′,6′‐Dihydroxy‐4,4′‐dimethoxychalcone, for instance, cyclized to give the naturally occurring naringenin‐4′,7‐dimethyl ether in up to 64 % ee at 81 % conversion. The catalysis shows a marked dependency of the enantiomeric excess of the product on the catalyst, solvent and reactant concentration. Based on these successful examples of asymmetric cyclizations of 2′‐hydroxychalcones to flavanones, requirements for more active asymmetric catalysts can be defined.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Section: Introductionmentioning

confidence: 99%

Asymmetric Cyclization of 2′‐Hydroxychalcones to Flavanones: Catalysis by Chiral Brønsted Acids and Bases

2007

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Synthesis, Biological Evaluation and In Silico Metabolic and Toxicity Prediction of Some Flavanone Derivatives

Moorthy

Singh

et al. 2006

Chem. Pharm. Bull.

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Flavones, which are also known as anthoxanthins, are widely distributed as yellow coloured plant pigment (flavus, latin meaning yellow) and occur either in the free state or as glycosides associated with tannins. The derivatives of phenol present as glycosidal form and chemically they are derivatives of phenyl benzo-Y-pyrone (chromone) ring.1,2) The basic flavanoid structure is a flavone nucleus, which consists of 15 carbon atom, arranged in 2 rings labeled as A, B, C. In nature, they are available as flavone, flavonol, flavanone, isoflavone, chalcone and their derivatives. In acidic medium, it forms oxonium salts, which are very unstable in water and are hydrolyzed back to freebase. [3][4][5] Natural and synthetic flavanoids and flavanones have attracted considerable attention because of their interesting biological activity, including, antioxidant, antifungal, antibacterial, anti-inflammatory, antiasthmatic, antihypertensive, antiviral, estrogenic and diuretic activity.6-11) Flavanoids inhibit xanthine-oxidase enzyme and have superoxide-scavenging activities. Therefore they could be a promising remedy for human gout and ischemia by decreasing both uric acid and superoxide concentration in human tissues. 12)There are number of methods available for the synthesis of flavanoids and flavanones like Kostanecki method, 13,14) Allan-Robinson method, 15) Mahal-Venkataraman method, 16) the Chalcone method, the Wheeler method and others. Almost all the methods of synthesis of flavanones and flavanoids required more amount of heating during the reaction and the yields of the products obtained was less (50-60% yield). 17-19)The metabolic fate and toxicity of a molecule is highly dependent upon its structural elements. Exogenous chemicals entering a living system can undergo a number of chemical modifications by a wide array of enzymes, which use these chemicals as substrates. Rarely does a compound simply produce a single metabolite, in general, complex metabolic pattern of competitive and sequential reactions occur. Synthesis, Biological Evaluation and In Silico Metabolic and Toxicity Prediction of Some Flavanone DerivativesNarayana Subbiah Hari Narayana MOORTHY,* Rahul Jitendra SINGH, Hemendra Pratap SINGH, and Sayan Dutta GUPTA School of Pharmaceutical Sciences, Rajiv Gandhi Proudyogiki Vishwavidyalaya; Airport Bypass Road, Gandhi Nagar, Bhopal-462036, Madhya Pradesh, India. Received May 8, 2006; accepted June 29, 2006 Flavones chemically are anthoxanthins, occur either in the free state or as glycosides associated with tannins (flavanoids). Flavanoids (derivatives of flavone) possess various pharmacological activities and due to its xanthine-oxidase enzyme inhibitory effect it also has superoxide-scavenging activities. A series of 2-phenyl-2,3-dihydrochromon-4-one derivatives (flavanone derivatives) were synthesized from chalcones by cyclization method and their activities were evaluated against some gram positive and gram-negative bacteria. IR, NMR and CHN analysis confirmed the structure of the synthesized comp...

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Biomimetic Synthesis of the Flavanone Leridol, Revision of the Structure of the Natural Product

Cited by 2 publications

References 5 publications

Asymmetric Cyclization of 2′‐Hydroxychalcones to Flavanones: Catalysis by Chiral Brønsted Acids and Bases

Asymmetric Cyclization of 2′‐Hydroxychalcones to Flavanones: Catalysis by Chiral Brønsted Acids and Bases

Synthesis, Biological Evaluation and In Silico Metabolic and Toxicity Prediction of Some Flavanone Derivatives

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