Isolation and Characterization of Biogenetically Related Highly Oxygenated Nortriterpenoids from <i>Schisandra chinensis</i>

Pre-schisanartanin (1) and schindilactones A−C (2−4) were isolated from Schisandra chinensis. Among them, compound 1 had an unprecedented carbon skeleton. More importantly, the structure features of this compound provided new insight into the biosynthesis of triterpenoids with schisanartane skeleton. Their structures were determined by extensive spectroscopic analysis, single-crystal X-ray diffraction, and on the basis of the absolute structure of one related nortriterpenoid (5), which was determined for the first time by a modified Mosher method.