60 1,2-結合オリゴ糖配糖体の^<13>C-NMR

概要

論文の詳細を見る
The anomalous glycosylation shifts(GS) of signals due to an anomeric carbon of a glycosyl group as well as an O-glycosylated carbon(C-2) of a glycosylated glucoside moiety were sometimes observed for a 2-O-β-D-glucosyl(or -β-D-xylosyl)-β-D-glucoside unit of some of the oligoglycosides (examples: ginsenoside-Rf(7) and chikusaikoside-I(11) etc.), being explained in terms of change of the angles of the glycosyl linkages owing to the strong steric interaction between 2-O-glycosyl and 1-O-aglycone(or -sugar) bonds. A variety of 2-O-glycosylated α- and β-L-arabinoside (pyranoside form) were synthesized. In contrast to the above case, all of 2-O-β-D-glucosylation, β-D-xylosylation and α-L-arabinosylation of α-L-arabinosides resulted in remarkable upfield shifts of C-3, -4 and -5 signals and significant decrease of ^3J_<H1-H2> of an anomeric proton signal of the glycosylated arabinoside moiety besides GS of C-1 and -2, demonstrating the increase of the contribution of ^1C_4 conformation for the ring structure of the glycosylated arabinoside moiety.(Tables I and II) On the other hand, no significant change of chemical shifts of C-3, -4 and -5 signals and of ^3J_<H1-H2> was observed for 2-O-α-L-rhamnosylation of α-L-arabinoside and 2-O-glycosylation of β-L-arabinosides as summarized in Tables III and IV, indicating the less contribution of ^1C_4 form in these cases.
天然有機化合物討論会の論文
1982-09-10