Novel spirobicyclic artemisinin analogues (artemalogues): Synthesis and antitumor activities.

The sesquiterpene lactone framework of artemisinin was used as a drug repositioning prototype for the development of novel antitumor drugs. Several series of novel artemisinin analogues (artemalogues) were designed and synthesized through 1,3-dipolar cycloaddition of artemisitene with nitrile oxides or nitrones. The isoxazolidine-containing spirobicyclic artemalogue 11b turns out to be the most potent with low micromolar IC₅₀ values against all three tumor cells, which were at least 4- to 14-fold more potent than the parent artemisinin.