Metarhizides A–C and metarhizosides A–B: PKS-NRPS macrolides and aromatic glycosides from an Australian fish gut-derived fungus, Metarhizium sp. CMB-F624

Abstract

Chemical and cultivation profiling of an Australian Mugil mullet gastrointestinal tract (GIT) derived fungus, Metarhizium sp. CMB-F624, prompted investigation of a scaled up rice grain cultivation leading to the discovery of three new PKS-NRPS macrolides, metarhizides A-C (1–3) featuring an unusual tautomerically labile α-methyl-β-keto-macrolactone, together with two new aromatic glycosides, metarhizosides A and B (4–5). Structures were assigned to 1–5 on the basis of detailed spectroscopic and chemical analysis, and biosynthetic considerations.