Jatropholane-type diterpenes from Euphorbia sikkimensis.

Four new jatropholane-type diterpenes (1-4), named sikkimenoids A-D, were isolated from the aerial parts of Euphorbia sikkimensis. The structural elucidations of 1-4 were accomplished by extensive NMR analyses, and their absolute configurations were established by ECD calculations. Compound 2 exhibited weak antiangiogenic activity with an IC50 value of 43.0 mu M when evaluated using a zebrafish model.