Schicagenins A–C: Three Cagelike Nortriterpenoids from Leaves and Stems of Schisandra chinensis

Schicagenins A–C (13), three unprecedented nortriterpenoids characterized with a tetracyclic oxa-cage motif and C9 side chain, were discovered from the leaves and stems of Schisandra chinensis. Their structures were determined on the basis of extensive spectroscopic analysis, and the absolute stereochemistries were established by single-crystal X-ray diffraction and CD experiments. A plausible biosynthetic pathway of 13 was also discussed.