A new cassane diterpenoid from the seeds of Caesalpinia decapetala.

Phytochemical investigation on the seeds of Caesalpinia decapetala led to the isolation of a new cassane diterpenoid with an unusual O bridge between C-19 and C-20, named phanginin Q (1), together with three known cassane diterpenoids, caesaljapin (2), caesaldekarin A (3), and caesaldekarin B (4). The structure of the new compound was elucidated by spectroscopic methods, including (1)H NMR, (13)C NMR, HSQC, (1)H - (1)H COSY, HMBC, NOESY, and HR-ESI-MS.