Pre-schisanartanins C–D and propintrilactones A–B, two classes of new nortriterpenoids from Schisandra propinqua var. Propinqua

Four new nortriterpenoids, pre-schisanartanins C and D (1–2) with pre-schisanartane backbone, and propintrilactones A and B (3–4) possessed wuweiziartane framework, were isolated from the acetone extract of the stems of Schisandra propinqua var. propinqua. Their structures were characterized by extensive spectroscopic analyses. Compounds 3 and 4 existed as a pair of slowly interconverting diastereomers at room temperature; their absolute configuration was established by CD methods. Compounds 1–4 showed no cytotoxicity against K562, A549, and HT–29 human cancer cells.