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.