Cyclodepsipeptides, α-Pyrone Derivatives and Secalonic Acids from Two Unidentified Freshwater Fungi (G100 and G102)

The chemical mycology of freshwater fungi is practically uninvestigated. In ongoing studies to explore fungi (Ascomycota) from freshwater habitats in North Carolina, eight compounds were isolated from organic extracts of two unidentified freshwater fungi (G100 and G102). Of these, two were cyclodepsipeptides [Sch 378161 (1) and Sch 217048 (3)], two belong to the secalonic acid family, the known dimeric [secalonic acid A (3)] and a new monomer [8,8a-dihydroerogchrome A (4)], and four α-pyrone derivatives, two known [phomopsinone A (5) and phomopsinone D (6)] and two new [phomopsinone E (7) and phomopsinone F (8)]. The structures of the isolated compounds were elucidated using a set of spectroscopic and spectrometric techniques (HRESIMS and ¹H, ¹³C, COSY, HSQC, HMBC, and NOESY NMR). The biological activities of these classes of compounds suggest that they afford a competitive advantage to the fungi.