Novel sesquiterpenoids from the fairy ring fungus, Marasmiusoreades

The structures of four new drimane-type sesquiterpenes 1–4 produced in liquid cultures of the fairy ring fungus, Marasmiusoreades, have been determined by a combination of chemical and spectroscopic methods. The structure assigned to one of these sesquiterpenes (1) has been confirmed by an X-ray crystallographic study. An unprecedented feature of all four sesquiterpenes is the biosynthetic elaboration of C8–C12 and C15 of the drimane skeleton to a dioxabicyclooctane moiety. In addition, two of the sesquiterpenes possess an uncommon α orientation of the hydroxyl groups at C3. Keywords: sesquiterpenes, fungal metabolites, drimanes, fairy ring mushroom, crystal structure.