Studies on the constituents of asclepiadaceae plants. LX. Further studies on glycosides with a novel sugar chain containing a pair of optically isomeric sugars, D- and L-cymarose, from Cynanchum wilfordi.

Abstract

Seven new glycosides named wilfosides D1N (7), K1N (8), M1N (9), F1N (10), W1N (11), W3N (12), and G1G (13) were isolated from Cynanchum wilfordi HEMSLEY (Asclepiadaceae), and their structures were deduced on the basis of spectral and chemical evidence. A unique feature is that 7-11 and 13, as well as wilfosides C1N (2), C2N (3), C1G (5), and C2G (6), each include both D-(22) and L-cymarose (23) in the sugar chain. L-Diginose (24) is also a constituent of their sugar chains. The carbon-13 nuclear magnetic resonance (13C-NMR) chemical shifts of methyl α-(24a) and β-L-diginopyranoside (24b) were assigned, and the conformations of 24a and its acetate were studied.