Caesalpinone A, a new type of gorgonane sesquiterpenoid containing an unprecedented 1,15-bridge, from the pods of Caesalpinia spinosa Kuntze.

Caesalpinone A (1), a new type of gorgonane sesquiterpenoid containing an unprecedented 1,15-bridge, along with ten known sesquiterpenoids (2−11) were isolated from the pods of Caesalpinia spinosa Kuntze (Tara). The structure of caesalpinone A was elucidated based on its 1D and 2D NMR spectra. The absolute configuration of 1 was assigned by the comparison of the experimental and calculated electronic circular dichroism spectra. Compound 1 was evaluated for the inhibitory activities against five human tumor cell lines. The sesquiterpenoids of isodaucane skeleton and caryolane skeleton were isolated from Caesalpinia genus for the first time. Compounds 5–9 were firstly reported from Tara.