38 メグスリノキより得られる2つの新しいヘテロサイド : diarylheptanolとarylbutanolのapiosylglucosides

抄録

Previously we reported the structure elucidation of aceroside I (4)(a glucoside of acerogenin A (3)), epirhododendrin (2)(a glucoside of (+)-rhododendrol (1)), and acerogenin B (5) isolated from the bark of Acer nikoense Maxim. Acerogenin A (3) is reportedly the first example of a diphenyl ether type of diarylheptanoids. Further investigation on the ingredients of the plant bark afforded several new glycosides, some of which are now designated as aceroside III (6), IV (7), V (8), and apiosylepirhododendrin (9). Firstly the assignment of chemical shifts of ^<13>C-NMR spectra of 3 and 2 was extensively studied in order to speed up the structure elucidation of their analogous substances. The results are summarized in Table I. Aceroside IV (7) was presumed to be 2-β-D-glucopyranoside of acerogenin C (15)(11-keto derivative of 3) on the basis of its NMR spectrum, which was confirmed by its chemical data. Aceroside V (8) seemed to be 9-hydroxyaceroside IV. On hydrolysis aceroside III (6) and apiosylepirhododendrin (9) afforded acerogenin A (3) and (+)-rhododendrol (1) as aglycone respectively, along with both glucose and apiose as sugar moiety. Partial hydrolysis of aceroside III (6) gave a monoglucoside (19) of 3. On the basis of combination of the chemical shifts in ^<13>C-NMR, PRFT-NMR, and the above chemical evidences, those glycosides (6,9) were elucidated to be β-D-apiofuranosyl (1→6)-β-D-glucopyranosides of acerogenin A (3) and (+)-rhododendrol (1) respectively. Chemical evidences of linkage-sites between apiose, glucose, and aglycones of 6 and 9 were finally obtained from methanolysis of the permethylated apiosylglucosides followed by identification of methylated sugars and aglycones on GLC and/or TLC.