94 タンニンの^<13>C NMR : 平衡混合物として存在するタンニン等

概要

論文の詳細を見る
The application of ^<13>C NMR to structural elucidation of the oligomeric hydrolyzable tannins of molecular weight 1500-3000 has been extended to the oligomers which are present as complex equilibrium mixtures of tautomers because of the presence of the anomeric hydroxyl group(s). The glucose carbon signals of tellimagrandin I (5), pedunculagin (6) and gemin D (7) which are the monomeric hydrolyzable tannins having anomeric hydroxyl group have been unambiguously assigned by the two-dimensional ^1H-^1H and ^1H-^<13>C shift correlation experiments. The 2D spectral analysis was then applied to rugosin E (8), a dimer which may biogenetically occur by the C-O oxidative coupling between 5 and tellimagrandin II (9), and the results revealed that each glucose carbon signal of 8 appears in the range of that of the monomeric units, 5 and 9, with discrepancy within 0.3 ppm. The complicated ^<13>C resonances of glucose moieties of dimers or trimers which exist as mixtures of 2-8 tautomers have thus been shown to be assigned based on the data of monomeric units. The structural assignments of oligomers of this class should be markedly facilitated by the application of these results, as it could be done without chemical degradation of oligomers, and actually have been successfully applied to the new oligomers, camptothin A (10), B (11) and oenothein B (13) which have been isolated from Camptotheca acuminata and Oenothera erythrosepala. The ^<13>C resonances of the ^1C_4 glucopyranose cores of geraniin (1), chebulagic acid (2) and corilagin (3), and those of open-chain glucose in the C-glucosidic ellagitannins, casuarinin (16) and consequently stachyurin (17) and casuariin (18), have been also assigned by the 2D spectra.
1985-09-07

94 タンニンの^<13>C NMR : 平衡混合物として存在するタンニン等

スポンサーリンク

概要

著者

関連論文

スポンサーリンク