H-1 and C-13 NMR study of copteroside E derivatives

The triterpenoid saponin copteroside E (1) was isolated from the flowers an d leaves of Verbesina suncho. Detailed H-1 and C-13 NMR assignment of its a cetyl derivatives 2 and 3 was achieved by 2D NMR techniques including COSY, TOCSY, NOESY, HMQC and HMBC. The presence of a glucuronolactone moiety in 2 is supported by the calculated vs observed H-1-H-1 coupling constants. Mo lecular mechanics calculations on 1 were useful for understanding the forma tion of glucuronolactone 2 and decaacetate 3, Copyright (C) 2000 John Wiley & Sons, Ltd.