88(P85) オリゴ糖類の構造解析 : アスパラガスの四糖の完全帰属(ポスター発表の部)

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Detailed analysis of the ^1H and ^<13>C NMR spectra of three fructose-oligosaccharides (1-3) isolated from Asparagus officinalis L. (Liliaceae) was carried out. All compounds consist of one unit of glucose and three units of fructose. The ^1H NMR signals of the compounds are severely overlapped in the region of δ_H 3.45-3.85ppm and the circumstances are the same in the ^<13>C NMR. It was quite difficult to make assignments of the signals using conventional NMR methods. Hence, overcoming these signal-overlapping problems required some special NMR techniques to be applied as follows. Assignments of each signal of C-5 and C-6 of the fructose residues which could not be separated in 2D spectra were achieved by 1D INAPT (Insensitive Nuclei Assigned by Polarization Transfer) method. Since δ_C of C-6 of the fructoses are close each other and H-6 of the fructoses are also present in the crowded region, those protons could not be assigned by HMQC or HIMBC spectrum because of limited resolution in the carbon axis of these methods. However, the limited δ_C range (less than 4ppm) of C-6 methylenes of the compounds enabled high resolution in the carbon axis when a methylene-selected HSQC method, a modified version of E-HSQC, was applied. Finally, quaternary C-2 of fructoses gave no correlations with H-3 and H-4 of the residues by HMBC or INAPT. In this case, heteronuclear ^<13>C {^1H} NOE experiments in which each of the H-3 was selectively excited or saturated were effective for their assignments.
天然有機化合物討論会の論文
1996-09-02

88(P85) オリゴ糖類の構造解析 : アスパラガスの四糖の完全帰属(ポスター発表の部)

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