Pullenvalenes E-H: Triterpenyl-Aminoglycosides from an Australian Soil-Derived Fungus, Clonostachys sp.

Chemical profiling of soil-derived microbes collected under the auspices of the Australian citizen science initiative Soils for Science detected two fungi, Clonostachys sp. S4S-07771A07 and Coccidiodes sp. S4S-14879B01, capable of producing pullenvalenes, a rare class of triterpene glycoside. Cultivation profiling followed by scaled up cultivation and fractionation of the former yielded the known pullenvalenes A-D (1-4) and the new analogues E-H (5-8), with structures secured by detailed spectroscopic analysis and biogenetic considerations. This study reveals that the pullenvalenes 1-8 are produced by several genera of fungi (Clonostachys, Coccidiodes and Talaromyces) recovered from different geographic locations and substrates. We also draw attention to structural and biosynthetic similarities with the known Red Sea sponge metabolites neviotines A-D (9-12) and abudinols A-B (13-14), prompting speculation that the latter may be products of sponge-associated fungi.