2 α-Coriofuranose : corioseの結晶中での構造と溶液中での変換

概要

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Coriose, isolated from Coriaria japonica A. Gray, was found to have the structure (I). Although this sugar is easily crystallized to yield one form of crystals, it is very rapidly converted to the equilibrated mixtures in the solution, as exhibited by the fast mutarotation and the transformation of the NMR spectra. On acylation of coriose with acyl chloride, pentabenzoate (XI) and pentaacetate (XIII) which are regarded as the furanoids are produced. However, mixtures containing the pyranoid acetate (XII) is obtained on the acetylation with acetic anhydride-pyridine. The α-furanose structure (Fig. 1) in the crystalline state, which is regarded as being unstable based on the conformational analysis, has been determined by the X-ray analysis. Determination of mutarotated coriose by the NMR spectra in DMSO-d_6, and by the gas chromatography of trimethylsilyl ethers of the pyridine solution, and also of the syrupy mixtures of coriose with other sugars and polyalcohols, has been attempted. The two-step trimethylsilylation of crystalline coriose leading to two final products as shown by VII→XIV→XV→XVI is also exhibited by the corresponding peaks in the gas chromatograms of trimethylsilylated products from the equilibrated coriose. Fairly high amounts of the furanoses and the keto-form in the equilibrated mixtures are exhibited by the NMR spectra and by the gas chromatograms.
天然有機化合物討論会の論文
1969-09-01