Flavylium chloride

Other methods of preparing flavone include the action of ethanolic alkali on 2 -acetoxy-a,/3-dibromochalcone 7 Claisen condensation of ethyl o-ethoxybenzoate and acetophenone, and cyclization of the resulting 1,3-diketone with hydriodic acid 8 and treatment of 3-bromoflavanone with potassium hydroxide in ethanol.9 Flavone has also been prepared from ethyl phenyl-propiolate by condensation with sodium phenoxide and subsequent cyclization with phosphorus pentachloride in benzene 10 by fusing o-hydroxyacetophenone with benzoic anhydride and sodium benzoate 11 by the dehydrogenation of 2 -hydroxychal-cone with selenium dioxide 12 and by the action of alkali on flavylium chloride.13... 

The fundamental nucleus in anthocyanidins (aglycones) is flavylium chloride. Most of the anthocyanidins are derivatives of 3,5,7-trihydroxyflavylium chloride. Thus, the hydroxylation patterns in the natural anthocyanidins fall into the three basic groups of pelargonidin, cyanidin and delphinidin. Anthocyanidins are rarely found in fresh plant material because of their instability [19]. 

Anthocyanins may have been eaten for around 7.5 million years since the beginning of mankind. Anthocyanins such as flavones and flavanones are the derivatives of 3,5,7-trihydroxy-flavylium chloride that could provide red, blue, yellow, purple and other colors of vegetables and fruits. 

The red and blue colors of many flowers and fruits are due to the anthocyanins, glycosides of pyrylium salts. The parent structure of the pyrylium salts is flavylium chloride which can be synthesized as follows ... 

Favorskil rearrangement of 2-chloro-cyclohexanone, 39, 37 Ferric chloride, 36, 31 37, 77 Ferric nitrate hydrate, 39, 73 Ferrocene, 36, 31, 34 Ferrous chloride solution in tetrahy-drofuran, 36, 31, 34 Fischer indole synthesis, of 1,2-benzo-3,4-dihydrocarbazole, 30, 91 of 1,2,3,4-tetrahydrocarbazole, 30, 90 Flavone, 32, 72 Flavylium chloride, 32, 75 Flow meter, 34, 7 Fluorene, 34, 32 39, 44 Fluorene, 9-methyl-, 39, 43 9-Fluorenecarboxylic acid, 33, 37 o-Fluorobromobenzene, 39, 75... 

Experimental structural results indicate that the unknown, PA-X, may have a structure similar to delphinidin, since the same substitution pattern was observed [82]. The absorption maxima of PA-X showed a 25 nm bathochromic shift upon the addition of A1C13, thus indicating the presence of an ortho-dihydroxyl group in the B-ring [84]. Further analysis suggests that PA-X may also be similar to 8-methoxy-7,3, 4 -trihydroxy-flavylium chloride and 3,8-dimethoxy-7,3, 4 -trihydroxyflavylium chloride which were isolated from the heartwood of Acaria saxatilis by Fourie et al. 

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