With natural (-)- carvone as starting material, we designed and synthesized altogether four cyclic enol ethers, the immediate precursors to the desired end products. These compounds exhibited entirely unexpected resistance to singlet oxygen, provding a valuable piece of previously unknown knowledge about the photosensitized oxidaion by molecula oxygen. The synthesis starting from (-) - menthol via a similar route as from (-)- carvone was successful, giving the corresponding C-nor-qinghaosu analogue as expected.

Key words: ARTEANNUIN, ANALOGUE, PHOTOOXIDATION, CARVONE, MENTHOL