1983/12/01 by Tokunaru Horie, Tokunaru Hòrie, Hiroki Kourai +1
Biochemistry, Genetics and Molecular Biology · Medicine · #Bioactive natural compounds #Biological Activity of Diterpenoids and Biflavonoids #Synthesis of Organic Compounds
paper · pdf · doi:10.1246/bcsj.56.3773
crossref issued 1983/12/01 · crossref published 1983/12/01 · crossref published-print 1983/12/01 · openalex publication_date 1983/12/01 · crossref published-online 2006/06/27 · crossref created 2006/07/26 · crossref deposited 2024/01/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/26 · crossref indexed 2026/07/30
Abstract The demethylation of seven 8-hydroxy-5,7-dimethoxyflavones with anhydrous aluminum chloride or bromide in acetonitrile was studied and the following results were obtained. (1) Anhydrous aluminum chloride in acetonitrile selectively split the 5-methoxyl group without cleavage of the 7-methoxyl group, and seven 5,8-dihydroxy-7-methoxy-flavones were quantitatively synthesized by the demethylation. (2) In the demethylation with anhydrous aluminum bromide, the 5- and 7-methoxyl groups on 4′,5,7-trimethoxy- and 3′,4′,5,7-tetramethoxy-8-hydroxyflavone were selectively split to give the corresponding 5,7,8-trihydroxyflavones in good yield. However, the demethylation was not accessible to the synthesis of 5,7,8-trihydroxy-3′,4′,5′-trimethoxyflavone, 4′,5,7,8-tetrahydroxy-3′-methoxy-, and 3′,5,7,8-tetrahydroxy-4′-methoxyflavone, because of the cleavage of the methoxyl groups on the B ring. The synthesized flavones were employed for the identification of the two natural flavones, which were proposed to be 4′,5,8-trihydroxy-7-methoxyflavone and 4′,5,8-trihydroxy-3′,7-dimethoxyflavone. The former, salvitin, was revised to 4′,5,7-trihydroxy-6-methoxyflavone and the latter seemed to be 4′,5,7-trihydroxy-3′,8-dimethoxyflavone.