7 エステル型配糖体の研究 : acanthopanax chiisanensisのA-セコトリテルペン配糖体の構造および2-0-グリコシルアラビノシルエステルの^<13>C-NMRについて

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1) A new ester-type glycoside, named chiisanoside(1) was isolated from stem bark of Acanthopanax chiisanensis(Araliaceae), a Korean folk medicine. On enzymic hydrolysis, 1 yielded a genuine aglycone named chiisanogenin(2), while mineral acid hydrolysis of 1 gave glucose, rhamnose and a modified aglycone(15). The sturcture of 2 was revealed by means of NMR spectrometry and chemical derivation in comparison with those of A-seco-betulinic acid(6) and its derivatives, and 1 was formulated as α-rhamnopyranosyl(1→4)-β-glucopyranosyl(1→6)-β-glucopyranosyl ester of 2 (Chart 1). 2) In part of our studies on the NMR of 2-linked arabinopyranosides, β-D-glucopyranosyl(1→2)- and α-L-rhamnopyranosyl(1→2)-α-L-arabinopyranosyl esters of 3-O-acetyloleanolic acid(16) and caprylic acid(17) were prepared using tert-butyl as a new protecting group of a terminal anomeric OH. As already observed for platycodins etc., the anomalous NMR signals of the esters of 16 indicated the remarkable increase of contribution of ^1C_4 form of its arabinopyranosyl ring especially for the α-rhamnosyl-α-arabinosyl ester, while the NMR signals of the esters of 17 showed no unexpected displacement, demonstrating little contribution of the ^1C_4 form (Table 4). 3) It was found that LiI and 2,6-lutidine in methanol cleaved selectively an ester-glycoside linkage without any undesirable change of a sugar moiety, affording a methyl oligo-glycoside from an ester type sugar unit in a high yield (Chart 7).
天然有機化合物討論会の論文
1983-09-15

7 エステル型配糖体の研究 : acanthopanax chiisanensisのA-セコトリテルペン配糖体の構造および2-0-グリコシルアラビノシルエステルの^<13>C-NMRについて

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