29 ジアゾメタンによる糖-アグリコン結合の開裂反応のメカニズムとキラヤサポニンの構造解明への応用

概要

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Mechanisum of the diazomethane degradation for the sugar-aglycone linkage of the gypsogenin 3-O-glycoside(1) was studied and the useful degradative reaction was applied to the structure determination of quillayasaponin. Since three kinds of functional groups of 1, the 4α-CHO group in the aglycone, COOH and 4-OH group in the glucuronic acid were presumed to contribute to the degradative reaction, the necessarity of the each functional group was examined using a model compound 7, and only the 4α-CHO group was showed to be essential. By taking the above evidence and the usual reaction products of aldehyde with diazomethane into account, the reaction must be proceeded through such a oxide intermediate as shown in the scheme 6. QS-III(25), a major acylated genuine bisdesmoside of the so-called quillayasaponin, afforded a 28-O-glycosidal triterpenoid(29) still possessing acyl moiety by this diazometane degradation. On the basis of chemical and spectral evidence, especially, comparison of the ^<13>C NMR spectra of 29 and its desacyl compound(30)(Table 1), the site of linkage of acyl moiety of 29 was determined. The structure of 25, therefore, was complex acylated oligosaccharide as shown in scheme 8.
天然有機化合物討論会の論文
1986-09-09