Three new C21-steroidal glycosides from the roots of Cynanchum inamoenum.

Three new C(21)-steroidal glycosides presenting an unusual 13,14:14,15-disecopregnane-type skeleton, named inamosides A-C (1-3), together with two known C(21)-steroidal glycosides, were isolated from the MeOH extract of the roots of Cynanchum inamoeum (Maxim.) Loes (Asclepiadaceae). The aglycone of compounds 1, 2, and 3 has a 2beta-hydroxyl, which has not yet been reported in the literature. The structure and relative configuration of the aglycone of compounds 1, 2, and 3 were established by X-ray crystallographic analysis.