Synthesis of antimalarial G-factors endoperoxides: relevant evidence of the formation of a biradical during the autoxidation step

In the search for new antimalarial endoperoxides related to G-factors series, using a methodology based on autoxidation of a dienol sytem, unexpected cyclic ether alcohols and hydroperoxides were obtained confirming the structure of the previously postulated biradical intermediate implicated in oxygen uptake. Antimalarial activities of PMB-endoperoxides are greatly enhanced when the peroxyhemiketal function is methylated for the G3 endoperoxide.