Cladobotric Acids: Metabolites from Cultures of Cladobotryum sp., Semisynthetic Analogues and Antibacterial Activity

Three new polyketide-derived natural products, cladobotric acids G-I(1-3), and six known metabolites (4,5,8-11) were isolated from fermentation of the fungus Cladobo-tryumsp. grown on rice. Their structures were elucidated by extensive spectroscopic methods. Two metabolites, cladobotricacid A (4) and pyrenulic acid A (10), were converted to a series of new products (12-20) by semisynthesis. The antibacterial activities of all these compounds were investigated against the Gram-positive pathogen Staphylococcus aureusincluding methicil-lin-susceptible (MSSA), methicillin-resistant and vancomycin-intermediate (MRSA/VISA), and heterogeneous vancomycin-intermediate (hVISA) strains. Results of these antibacterial assays revealed structural features of the unsaturated decalins important for biological activity