Phainanolide A (1),
a highly modified triterpenoid incorporating an unprecedented 6/9/6
heterotricyclic system and a highly oxygenated 5,5-spirocyclic ketal
lactone, along with three new triterpenoids 2–4 were isolated from Phyllanthus hainanensis. Their structures were completely elucidated by a combination of
diverse methods including 2D NMR, quantum chemical NMR and ECD calculations,
and NMR data analogy with model compounds. Compounds 1–4 exhibited both remarkable cytotoxic and immunosuppressive
activities.