15 アフリカ産植物中の発芽抑制物質Triumferolの構造及び合成

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The leaf extract of the east African folk medicinal plant Triumfetta rhomboidea (Tiliaceae) was found to exhibit antigermination activity against lettuce seeds. The active principle, named 'triumferol', was isolated, and its structure was determined to be 4-hydroxyisoxazole (1), a simple but hitherto unknown heterocyclic compound. The lettuce seed antigermination activity of triumferol was 100% at 100ppm and 70% at 50ppm. Attempts of synthesizing triumferol by the methods used in the synthesis of 3- or 3,5-substituted-4-hydroxyisoxazoles were fruitless; treatment of 4a, 4b, 5a, 5c, and 5d with hydroxylamine afforded no trace of 1; fulminic acid (6b) did not give the 1,3-dipolar adduct (8b); a Sandmeyer-type reaction of 13 produced nothing but water soluble materials. The synthesis of triumferol was finally achieved through three steps of reactions; conversion of the known acid (19) into the acid chloride (20), a Grignard reaction of 20 with methyl-magnesium iodide to give 17, and treatment of 17 with a mixture of 30% H_2O_2 and conc. H_2SO_4 (1:1.3v/v) to afford 1 in 50% overall yield.
天然有機化合物討論会の論文
1981-09-10