Agrimonolide (竜牙草の一新成分) の化学構造 (第1報)

抄録

A new phenolic lactone, m.p. 173.5°, was isolated from the fresh subterranean part of Agrimonia pilosa LEDEB. and was named agrimonolide (I). Molecular formula of (I) agrees with C₁₈H₁₈O₅, possessing one methoxyl and two phenolic hydroxyls, one of which is chelated to a lactonic C=O and is not easily methylated. It is a γ- or δ- lactone and the acid obtained on cleavage of the lactone ring easily undergoes decarboxylation to form a compound of m.p. 169°, C₁₇H₂₀O₄, which was named agrimonol.
Bromination of (I) easily afforded a dibromo (VI) and tribromo (VII) derivatives, while oxidation of (I) and (VI) gave anisic acid (VIII). Oxidation of (VII) afforded 3-bromo-4-methoxybenzoic acid. Oxidation of the dimethyl derivative of (I) formed anisic acid and 3, 5-dimethoxyphthalic acid (XIII). Since potassium salt of the acid obtained on lactone-cleavage of (IV) is levorotatory, it is clear that asymmetric carbon is present in (I). There is no C-methyl group in (I). It was thereby concluded that the structure of agrimonolide would correspond to one of the formulae (XVI), (XVII), and (XVIII).