An ursadienedioic acid glycoside from Crossopteryx febrifuga

From the root bark of Crossopteryx febrifuga a triterpene saponin characterized by a novel ursadienedioic acid aglycone part was isolated. The structure 3β-(α-l-rhamnopyranosyloxy)-28-O-(β-d-glucopyranosyl)urs -12,20(30)-diene-27,28-dioic acid was established on the basis of 1H and 13C NMR, and mass spectrometry of various derivatives prepared before and after acidic cleavage of the 28-O-glucosyl ester. Total acidic hydrolysis led to hydration of the exocyclic 20(30)-double bond and further transformations of the aglycone group. © 1991.