Cladospirones B to I from Sphaeropsidales sp. F‐24′707 by Variation of Culture Conditions

Abstract

Variation of the culture conditions − static surface cultures in particular − of the fungus Sphaeropsidales sp. (strain F-24′707), which produces cladospirone bisepoxide (1), led to the isolation of eight new spirobisnaphthalenes − the cladospirones B to I (8−15) − together with seven known representatives of this class of secondary metabolites. Cladospirones C (9) and D (11) show antibiotic activity against bacteria and algae. The structures of cladospirone B (8) and E (12) were confirmed by X-ray structure analysis. Cladospirones C (9) and G to I (10, 14−15) represent new members of the spirobisnaphthalene family, thanks to their hydroxylation patterns. Moreover, they underline the extraordinary status of this interesting class of compounds as the most diverse secondary metabolites, allowing for their small number of carbon atoms, described to date. Almost all possible permutations of stereochemistry and oxygen substitution pattern on the C10 skeleton are produced by different fungi.