Nuclear oxidation in flavones and related compounds - Part XX. Oxidation of gossypetin to 6∶8-dihydroxy quercetin
V V Sreerama Murti T R Seshadri
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The two stage process of ortho-oxidation is applied to partial methyl ethers of gossypetin in order to introduce a new hydroxyl in the 6 position. The pentamethyl ether with a free hydroxyl in the 7- position does not react with hexamine. On the other hand, its isomer with a free 5-hydroxyl yields a mixture of products, one of which is the 6-aldehyde which could be oxidised by means of hydrogen peroxide. A more satisfactory procedure is to use the tetramethyl ether having the 5 and 8 hydroxyls free. It yields only the 6-aldehyde and subsequent oxidation with hydrogen peroxide leads to the formation of 5∶6∶8-trihydroxy compound. The products are useful partial methyl ethers and yield 6∶8-dihydroxy-quercetin on demethylation and its heptamethyl ether on methylation.
V V Sreerama Murti1 T R Seshadri1