Four new cyathane-type diterpenoids, nigernins C-F (1–4), together with four known compounds, were isolated from the fruiting bodies of the basidiomycete Phellodon niger. The structures of these new compounds were established on the basis of spectroscopic analysis, including 1D and 2D NMR experiments. In addition, nigernin F (4) with an unusual 3,4-seco cyathane diterpenoid skeleton was found to occur in nature for the first time. It was suggested to be as an oxidation product of C-3-C-4 bond cleavage of nigernin E (3).
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