New polyketides from a fungicolous isolate of Pestalotiopsis disseminata

Abstract

In the course of our studies of mycoparasitic and fungicolous fungi, an isolate (MYC-710 = NRRL 62562) was obtained from the surface of a basidioma of Stereum complicatum in Georgia. The culture was identified by micromorphology and partial sequence analysis as Pestalotiopsis disseminata. Pestalotiopsis spp. are known to be prolific sources of structurally diverse secondary metabolites. An ethyl acetate extract of rice fermentation cultures showed antifungal activity and was subjected to chemical investigation. Although the original activity was not recovered, these studies afforded seven new polyketides (disseminins A – E and spiciferones D and E) and a related compound previously known only as a synthetic product. The structures of these compounds were determined mainly by analysis of HRMS and NMR data. Unusual bis-tetrahydrofuran and dioxabicyclo[3.2.1]octane ring systems were identified for disseminins A and B, respectively. X-ray crystallographic analysis of the p-bromobenzoate derivative of disseminin A confirmed the structure and enabled assignment of its absolute configuration.