Selacyclicbiflavone A, an unusual macrocyclic biflavone from Selaginella uncinata (Desv.) Spring

Abstract

An unusual macrocyclic biflavone, selacyclicbiflavone A (1), have been isolated from Selaginella uncinata. The structure was elucidated on the basis of rigorous spectroscopic analysis including 1D and 2D NMR experiments as well as HRESIMS techniques. The absolute stereochemistry of compound 1 was further confirmed by comparing experimental data with calculated electronic circular dichroism (ECD) spectra. This is the first report of the macrocyclic biflavone with an unprecedented methylene bridge. A possible biosynthetic pathway was also postulated.