Arteannuin(Qinghaosu)(1)is a very potent natural antimalarial isolated from theChinese medicinal herb,Artemisia annua L.(Qinghao).Its chemical structure elucidation andtotal synthesis have already been achieved.In view of its unusual sesquiterpene structureof an endoperoxide ketal-acetal lactone and its specific biological activity,the authours havebeen studying the problem of the biosynthesis of 1 since 1984.From the consideration of thegeneral isoprene principle in the biogenesis of the sesquiterpene and the finding of all the iso- Arteannuin (Qinghaosu) (1) is a very potent natural antimalarial isolated from the Chinese medicinal herb, Artemisia annua L. (Qinghao) .Its chemical structure elucidation and total synthesis have already been. In view of its unusual sesquiterpene structure of an endoperoxide ketal-acetal lactone and its specific biological activity, the authours havebeen studying the problem of the biosynthesis of 1 since 1984. More about thisgeneral isoprene principle in the biogenesis of the sesquiterpene and the finding of all the iso-