シラネアオイの根茎の成分研究(第2報) : Glaupalolの全合成

概要

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For the synthesis of glaupalol, a new type of furanocoumarin isolated from the rhizomes of Glaucidium palmatum SIED. et ZUCC., attempts were made without success to prepare the intermediate, 1-(3,6-dihydroxy-2-methyl) phenyl-3,3-dimethyl-4-penten-1-one (2) which is obtained on alkaline fusion of glaupalol and can be reconverted into glaupalol by its carboxylation with dimethyl carbonate and sodium hydride. On the other hand, the Claisen rearrangement of synthesized 4-(3,3-dimethylallyloxy)-6-methoxy-5-methylcoumarin (45) in N-methylpiperidine leads to the formation of O-methylglaupalol (4) which is readily converted into glaupalol (1) with boron tribromide in methylene chloride. The key intermediate (45) was synthesized from 6-hydroxy-2-methylbenzoic acid (29). Potassium persulfate oxidation of the acid (29) gives the toluhydroquinone carboxylic acid (30) which is partially methylated with methyl iodide and potassium carbonate to furnish 6-hydroxy-3-methoxy-2-methylbenzoic acid (33). Treatment of the O-acetate (38) of this acid with thionyl chloride followed by diethyl malonate in the presence of lithium hydride, and subsequent hydrolysis with acetic acid yields 4-hydroxycoumarin (3) which is converted into the dimethylallyl ether (45) using its silver salt and 1-bromo-3-methyl-2- butene. Synthetic glaupalol was identical in all respects with natural glaupalol.
公益社団法人日本薬学会の論文
1971-02-25