Ambuic Acid and Torreyanic Acid Derivatives from the Endolichenic Fungus Pestalotiopsis sp.

Six new ambuic acid (1) derivatives (2-7) and a new torreyanic acid analogue (8) have been isolated from the crude extract of endophytic fungus Pestalotiopsis sp. inhabiting the lichen Clavaroids sp. The structures of these compounds were elucidated primarily by NMR and MS methods, and their absolute configurations were assigned by application of the CD excitation chirality method. Compounds I and 2 displayed antimicrobial activity against the Gram-positive bacterium Staphylococcus aureus.