Two known sesquiterpene lactones dehydroleucodine (1) and leucodine (2) were isolated from Gynoxys verrucosa, an herb used in traditional medicine in Southern Ecuador. Their anti-leukemic activity was determined against nine cell lines. Compound 1 showed LD50s between 0.11 and 3.99µM while compound 2 showed no activity, suggesting that the exocyclic conjugated methylene is required for the activity. In an effort to develop more water-soluble analogues of dehydroleucodine, adducts 3-6 were synthesized by a stereoselective conjugate addition of amines to the α-methylene-(γ-lactone moiety. The derivatives showed very low anti-leukemic activity. The structure of all compounds was established by spectroscopic methods and single-crystal X-ray crystallography.
