Metabolites of the fairy ring fungus, Marasmiusoreades. Part 2. Norsesquiterpenes, further sesquiterpenes, and agrocybin

Abstract

The fungus Marasmiusoreades has previously been reported to produce the sesquiterpenes marasmone (1), anhydromarasmone (2), isomarasmone (3), and dihydromarasmone (4) when grown in liquid culture. We report herein several other sesquiterpene metabolites of the same skeleton but with differing oxidation patterns. The norsesquiterpenes O-formyloreadone (15a), 3α-hydroxyoreadone (15c), and dehydrooreadone (17b) are also reported. It is suggested that the formyl group in 15a is derived biogenetically from C-15 of a precursor sesquiterpene. Oxidation of 1α, 15-dihydroxymarasmene (13a), one of the new sesquiterpenes reported, with one equivalent of pyridinium dichromate gives O-formyloreadone (15a) as one of the products. Agrocybin (5), a polyacetylene amide previously isolated from the fungus Agrocybedura, has also been isolated from the cultures of M. oreades. It is suggested that agrocybin (5) is the phytotoxic compound responsible for the killing of grass caused by the fairy ring mushroom fungus. Keywords: sesquiterpenes, fungal metabolites, drimanes, fairy ring mushroom, agrocybin.