New Highly Oxygenated Germacranolides from Carpesium divaricatum and their Cytotoxic Activity.

Eight highly oxygenated germacranolides (1-8) including four new ones (2-5) were isolated from the whole plant of Carpesium divaricatum. The planar structures and relative configurations of the new compounds were determined by NMR experiment and HRESIMS data. The absolute configuration of 1 was established by circular dichroism (CD) method and X-ray diffraction, and the stereochemistry of the new compounds 2-5 were determined by similar CD spectra with 1. Compound 2 is the first hydroperoxyl germacrane from the genus Carpesium. The (13)C NMR data of 1, NMR data of 6-7, and their absolute configurations were reported for the first time. Two new compounds (2 and 4) and two known compounds (6 and 8) exhibited potent cytotoxicity against human cervical cancer (HeLa) cells, superior to that of the positive control doxorubicin.