Diterpenoids and phenanthrenones from the leaves and stems of Strophioblachia fimbricalyx

Five new compounds, namely fimbricalyxoids A–D (1–4) and 13-O-methylfimbricalyx B (5), together with five known compounds (6–10) were isolated from the leaves and stems of Strophioblachia fimbricalyx. Fimbricalyxoid A (1), a cleistanthane diterpenoid, possesses a rare 3,20-oxybridge, while fimbricalyxoids C–D (3–4) are the first seco-ring-A pentanorditerpenoids. Their structures and absolute configuration were established based on NMR and MS data and ECD calculation (1). Compounds 1, 6, and 7 exhibited cytotoxicity against five human tumor cell lines with IC50 values in the range of 1.4–8.2 μM.