Lactonecembranoids from Croton laevigatus

Six new cembranoids, laevigatlactones A−F (16), and the known compound neocrotocembraneic acid (7) were isolated from leaves of Croton laevigatus. Their structures were elucidated on the basis of spectroscopic analysis, and that of 1 was confirmed by X-ray crystallography. Compound 2 exhibited modest cytotoxicity against HeLa cells, with an IC50 value of 38.4 μM.