Studies of the Selective O-Alkylation and Dealkylation of Flavonoids. XXIII. Demethylation Behaviors of 6-Hydroxy-4', 7-dimethoxy-5-tosyloxyflavones with Anhydrous Aluminum Halides in Acetonitrile
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概要
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In the demethylation of 6-hydroxy-3,4', 7-trimethoxy-5-tosyloxyflavone (1) with anhydrous aluminum bromide (AlBr_3) or anhydrous aluminum chloride-sodium iodide (AlCl_3-NaI) in acetonitrile, the elimination of the 5-tosyloxy group proceeded after demethylation to give 8-bromo-3,6,7-trihydroxy-4'-methoxyflavone (6) or 3,6,7-trihydroxy-4'-methoxyflavone (5) as a main product. The demethylation of 6-hydroxy-4', 7-dimethoxy-5-tosyloxyflavone (2) with AlCl_3-NaI also afforded 6,7-dihydroxy-4'-methoxyflavone (12), but that with AlBr_3 afforded 8-bromo-5,6,7-trihydroxy-4'-methoxyflavone (13) as a main product. The demethylation of 1 with anhydrous aluminum chloride (AlCl_3) was accompanied by migration of the tosyl group to give a mixture of 3,6-dihydroxy-7,4'-dimethoxy-5-tosyloxyflavone (3) and 5-hydroxy-3,4', 7-trimethoxy-6-tosyloxyflavone (9), but that of 2 proceeded after the cleavage of the 5-tosyloxy group to give a mixture of 5,6-dihydroxy-7,4'-dimethoxy- (14) and 5,6,7-trihydroxy-4'-methoxyflavones (15) other than the corresponding 6-tosyloxyflavone (16). In the demethylation of the acetates of 1 and 2 with AlCl_3,the cleavage of the 5-tosyloxy group proceeded prior to the demethylation to afford the corresponding 5,6,7-trihydroxyflavones (8 and 15), although the demethylation of the former acetate was accompanied by formation of 3,5,7-trihydroxy-4'-methoxy-6-tosyloxyflavone (10). Mechanisms are proposed for these reactions.
- 公益社団法人日本薬学会の論文
- 1997-10-15
著者
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Yamashita Kazumi
Faculty Of Pharmaceutical Sciences Okayama University
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TSUKAYAMA Masao
Department of Chemical Science and Technology, Faculty of Engineering, The University of Tokushima
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KAWAMURA Yasuhiko
Department of Chemical Science and Technology, Faculty of Engineering, The University of Tokushima
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YAMASHITA Kazuyo
Department of Chemical Science and Technology, Faculty of Engineering, The University of Tokushima
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Tsukayama M
Department Of Chemical Science And Technology Faculty Of Engineering The University Of Tokushima
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Tsukayama Masao
Department Of Chemical Science And Technology Fachnology Faculty Of Engineering The University Of To
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Yamashita K
Department Of Chemical Science And Technology Faculty Of Engineering The University Of Tokushima
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HORIE Tokunaru
Midori Kagaku Co., Ltd.,
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OHTSURU Yoshizumi
Midori Kagaku Co., Ltd.,
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MINAMIMOTO Noriko
Department of Chemical Science and Technology, Faculty of Engineering, The University of Tokushima
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Horie T
Midori Kagaku Co. Ltd.
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Minamimoto Noriko
Department Of Chemical Science And Technology Faculty Of Engineering The University Of Tokushima
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Tsukayama M
Univ. Tokushima Tokushima Jpn
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Kawamura Y
Department Of Chemical Science And Technology Faculty Of Engineering The University Of Tokushima
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Kawamura Yasuhiko
Department Of Chemical Science And Technology Faculty Of Engineering The University Of Tokushima
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Ohtsuru Yoshizumi
Midori Kagaku Co. Ltd.
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Tsukayama Masao
Department Of Biological Science And Technology The University Of Tokushima Graduate School
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Kawamura Yasuhiko
Department of Applied Chemistry, Faculty of Engineering, Tokushima University
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