Arteannuin (1) was a new sesduiterpenoid containing a, peroxide linkage and ie the antimalarial principle isolated from Artemisia amnua L.The present investigation deals with the synthesis of its analog 8, which contained tho peroxide moiety in the molecule, starting from arteannuinic acid (2) through photo-oxidation. The key intermediate 5 was obtained from 2 via esterifioation, selective NaBH₄ reduction and alkaline hydrolysis. Irradiation of a dilute pyridine elution of 6 in the presence of oxygen and a sensitizer (hematoporphyrin) with 200W high pressure mercury lamp gave the a-hydroperoxide 6. Ozonolysis of 6 in diohloromethane-pyridine afforded the aoetal 7. Activation of the carboxyl group in 7 with TsCl-Et₃N resulted in the cyolization of the lactone ring, to afford the final product, arteannuin analog 8.