Cynanosides A–J, ten novel pregnane glycosides from Cynanchum atratum

Four novel 13,14:14,15-diseco-18-nor-pregnane-type steroidal glycosides, cynanosides A–D (), and six novel 13,14:14,15-diseco-pregnane-type steroidal glycosides, cynanosides E–J () were isolated from the roots of Cynanchum atratum, together with one known compound, cynatratoside F (). Their structures including the absolute stereochemistry were determined on the basis of spectroscopic analysis and chemical evidence, with combination of the modified Mosher method, the exciton chirality method and chemical transformations.