Flavone 30 reduction

Ceroplastol synthesis, 1, 428 Cetyl alcohol synthesis, 1, 478 Chaetoglobasins structures, 4, 376 Chalcone, o -azido-2 -oxy-synthesis, 3, 823 Chalcone, 2-hydroxy-reduction, 3, 751 Chalcone, 2 -hydroxy-mass spectra, 3, 618 Chalcone dibromides flavone synthesis from, 3, 823 Chalcones polymers, 1, 304 Chanoclavine synthesis, 6, 423 Charge density waves in stacks of ions, 1, 351-352 Chartreusin... 

The application of flavonoids for the treatment of various diseases associated with free radical overproduction is considered in Chapter 29. However, it seems useful to discuss here some studies describing the activity of flavonoids under certain pathophysiological conditions. Oral pretreatment with rutin of rats, in which gastric lesions were induced by the administration of 100% ethanol, resulted in the reduction of the area of gastric lesions [157]. Rutin was found to be an effective inhibitor of TBAR products in the gastric mucosa induced by 50%i ethanol [158]. Rutin and quercetin were active in the reduction of azoxymethanol-induced colonic neoplasma and focal area of dysplasia in the mice [159], Chemopreventive effects of quercetin and rutin were also shown in normal and azoxymethane-treated mouse colon [160]. Flavonoids exhibited radioprotective effect on 7-ray irradiated mice [161], which was correlated with their antioxidative activity. Dietary flavones and flavonols protected against the toxicity of the environmental contaminant dioxin [162], Rutin inhibited ovariectomy-induced osteopenia in rats [163],... 

The stereoselective epoxidation of chalcones, followed by acid-catalysed ring closure and concomitant cleavage of the epoxide ring, provides a very efficient route to chiral flavon-3-ols and, subsequently, by borohydride reduction to produce flavan-3,4-diols [13, 14], It has been shown that diastereoselective reduction of the chiral flavon-3-ols by sodium borohydride in methanol yields the trans-2,3-dihydroxy compounds, whereas borohydride reduction in dioxan produces the cis-isomers [14] the synthetic procedure confirms the cis configuration of the 2,3-hydroxy groups of naturally occurring leucodelphinidins [14]. 

Modification of the substitution pattern on the same chromone gives a compound with smooth muscle relaxant activity, flavoxate (184). The synthesis of this flavone ester is initiated with methylation of the hydroxypropiophenone 177 to 178 followed by reduction of the nitro group to yield aniline 179. 

Nagarajan P, Sulochana N, Muralidharan VS (2004) Cyclic voltammetric reduction of 7 -hydroxy and acetoxy flavones at glassy carbon electrode. BuU Electrochem 20 93-96. 

Nitration of hydroxypropiophenone (7-1) followed by conversion of the phenol to its methyl ether by means of methyl iodide provides the intermediate (7-2) the nitro group is then reduced to the corresponding amine (7-3) by catalytic reduction. The newly introduced amine is then replaced by a nitrile group by successive conversion to the diazonium salt by means of nitrous acid followed by treatment with cuprous cyanide (7-4). Reaction with aluminum chloride removes the methyl ether to afford the ortho acylphenol (7-5). This is converted to the chromone (7-6) as above by reaction with benzoyl chloride and sodium benzoate. The nitrile is next hydrolyzed to the carboxylic acid (7-7) by means of sulfuric acid. The acid is then converted to its acid chloride by means of thionyl chloride and that treated with 2-(A -piperidyl)ethanol (7-8). There is thus obtained flavoxate (7-9) [8], a muscle relaxant whose name reflects its flavone nucleus. 

Flavanones arise from flavones after reduction of the double bond in the heterocycle (position C2/C3), Fig. (7). 

Metal hydrides usually reduce the carbonyl to alcohol but LAH converts xanthone into a dixanthyl ether (454) or xanthene (453) according to the conditions. The latter product is also obtained by the Wolff-Kishner-Huang-Minlon reduction. Metal-liquid ammonia opens the pyran-4-one ring of chromones and flavones to form dihydrochalcones and other compounds (79JOC1494). 

Both chemical and catalytic methods are available to convert chromanones to chromans, and flavones to flavans. Clemmensen s method is the most commonly used and usually gives good yields, but diborane is sometimes preferable. The Wolff-Kishner method appears to degrade the pyran ring and is rarely used on chromanones. The conditions of catalytic reduction have to be rather more drastic in order to produce chromans and flavans but much depends on the activity of the catalyst and on the solvent used. If the chromanol is first formed, more severe conditions are usually required to complete the reduction (77HC(31)207>. 

Generally, nucleophilic attack of chromones opens the pyranone ring. However, the reduction of flavone by LAH yields 4//-flavene (2-phenylchrom-2-ene) (62CI(L)1793). 

Whilst the reduction of flavones to flavanones is of little practical significance, isoflavones are easily reduced to isoflavanones. However, carefully controlled conditions are necessary if further reduction to isoflavanols and even isoflavans is to be avoided (7lJCS(C)1994). 

Lens aldose reductase has been implicated in the pathogenesis of cataracts in diabetic and galac-tosemic animals. The enzyme catalyzes the reduction of glucose and galactose to their polyols, which accumulate in large quantities in the lens and ultimately lead to mature lens opacities. Several key bioflavones have activity against this enzyme. Oral administration of quercitrin decreased the accumulation of sobital in the lens. Therefore, the accumulation of lens opacities could be partially abrogated by certain flavonoids. In a study of 30 flavones, 4 isoflavones, and 13 coumarins, many potent inhibitors were found, but 5,7,3, 4 -tetrahydroxy-3,6-dimethoxyflavone and 6,3, 4 -trihy-droxy-5,7,8-trimethoxyflavone were especially active. 

FMCa Flavonols Flavones Flavanones 24-26-28 9131 M-F Reduction of total mortality, lung cancer, prostate cancer arthritis, asthma, coronary heart disease (161-163)... 

ATBC Flavones Flavonols 6.1 25,732 M Reduction of fatal myocardial infarction, no reduction of stroke (167,168)... 

ATBCa Flavonols Flavones 6.1 27,110 M Reduction of lung cancer (169)... 

IWHS Catechins Flavonols Flavones 13 32,857 F Reduction of coronary heart disease, no reduction of stroke, reduction of rectal cancer (170-173)... 

WHS Flavanols Flavones 6.9 38,445 F No association with reduction of cardiovascular disease (174)... 

Chromones, flavones, and isoflavones of general types 396 and 398 have been reported to undergo reduction with nickel borohydride in dry methanol at ambient temperatures to give the corresponding 277-l-benzopyran-4-ols in good yields. In all cases studied, the products obtained were found to be the air-stereoisomers, for example, 397 and 399 (Scheme 64) <2002JCM201>. 

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