Maximumins A–D, Rearranged Labdane-Type Diterpenoids with Four Different Carbon Skeletons from <i>Amomum maximum</i>

Four highly rearranged labdane-type diterpenoids, maximumins A–D (1–4) possessing different new carbon skeletons, together with a biosynthetically related known analog 5 were isolated from Amomum maximum. The structures of new compounds with absolute configurations were characterized by spectroscopic and computational approaches. The plausible biogenetic pathways for 1–4 were proposed. These compounds showed moderate to weak activities against nuclear factor kappa B (NF-κB).