つばき実のサポニンの研究 (第3報)

サポゲノール並びに誘導体の酸化

抄録

Chromic acid oxidation of camellia-sapogenol in glacial acetic acid solution gave crystals of m.p. 254-258° (decomp.) (corr.), [α]_D¹⁸: 0° (c=0.405, CHCl₃), whose analytical values agreed with those of a tetrone compound, C₃₀H₄₂O₄. Similar chromic acid oxidation of isopropylidene-sapogenol gave crystals of m.p. 240-245° (decomp.) (corr.), [α]_D¹⁸: +113.2° (c=0.265, CHCl₃), whose elemental analysis indicated it to be the dione compound, C₃₃H₅₀O₄. Since the chromic acid oxidation product of sapogenol does not possess acid, aldehyde, hydroxyl, or lactone grouping, all four hydroxyls in sapogenol are assumed to be secondary hydroxyls. Oxidation of diacetylisopropylidene sapogenol in glacial acetic acid solution with selenium dioxide gave crystals of m.p. 234-234.5° (corr.), [α]_D¹⁸: 0° (c=0.135, CHCl₃), λ_max 251mμ, corresponding to the diene compound, C₃₇H₅₆O₆. Similar oxidation of triterpenes of α- and β-amyrin series with selenium dioxide resulted in complete recovery of the α-amyrin series but facile dehydrogenation occured in those of β-amyrin series to the diene compound with maximum absorption at 251mμ, from which it was assumed that camellia-sapogenol belonged to the triterpene of β-amyrin series, rather than that of α-amyrin series.