Trefolane A, a sesquiterpenoid with a new skeleton from cultures of the basidiomycete Tremella foliacea.

Trefolane A (1), an unprecedented skeleton with a 5/6/4 tricyclic ring system, was isolated from cultures of the basidiomycete Tremella foliacea. The structure was elucidated by means of spectroscopic methods and further confirmed by single crystal X-ray diffraction analysis. A possible biogenesis for trefolane A (1) was also proposed.