Schisanartane nortriterpenoids with diverse post-modifications from Schisandra propinqua.

Twenty-one highly oxygenated nortriterpenoids with a schisanartane skeleton were isolated from the stems of Schisandra propinqua var. propinqua. These nortriterpenoids featured a polycyclic framework composed of 7/8/5 consecutive carbocycles, which were organized by similar 5/5/7/5/7/5 rings A-F and varied oxygen-containing rings G and H. A biosynthetic classification of these compounds is proposed on the basis of their diverse post-modifications.