Photooxidation Products from a Marine Cadinane Sesquiterpenoid

To show that artifacts can readily form during research on marine natural products, a common marine sesquiterpenoid 1 was treated with sunlight in the presence of a pigment. Another set of solutions were prepared and kept in shade under the bench for two weeks as negative controls. As a result, four oxygenated derivatives 2–5 were obtained. A unique structure of a highly oxidized molecule 5 was solved by X-ray crystallography.