Bioactive asterric acid derivatives from the Antarctic ascomycete fungus Geomyces sp.

Five new asterric acid derivatives, ethyl asterrate (3), n-butyl asterrate (4), and geomycins A-C (6-8), have been isolated from cultures of an isolate of the Antarctic ascomycete fungus Geomyces sp. The structures of these metabolites were elucidated by NMR spectroscopy. The absolute configuration of 8 was determined by application of the CD excitation chirality method. Compound 7 displayed antifungal activity against Aspergillus fumigatus, whereas 8 showed antimicrobial activities against gram-positive and gram-negative bacteria.