Selenium dioxide promoted selenylation/cyclization of leucosceptrane sesterterpenoids.

A novel selenium dioxide promoted selenylation/cyclization of leucosceptrane sesterterpenoids was reported. Two types of leucosceptrane derivatives with different valence states of selenium atoms (Se 2+ and Se 4+ ) were obtained. The mechanisms of these two processes were proposed, and the selenium-containing derivates may serve as intermediates of Riley oxidation that could be trapped with appropriate substrates. Immunosuppressive activity screening revealed that 10 and 11 had obvious inhibitory effects on IFN-γ production, with IC 50 values of 5.29 and 17.60 μM, respectively, which were more active than their precursor leucosceptroid A.