Pseurotin A and 8-O-Demethylpseurotin A fromAspergillus fumigatusand Their Inhibitory Activities on Chitin Synthase

Two inhibitors of chitin synthase were isolated from submerged cultures of an osmophilic Aspergillus fumigatus strain and identified as pseurotin A (1) and its 8-O-demethyl derivative (2). The two compounds inhibited both the solubilized and the membrane-bound forms of the enzyme, but do not have antifungal or antibacterial activities. The IC50 of pseurotin A was 81 µM for the solubilized enzyme. 8-O-Demethylpseurotin was less active with an IC50 of 192 µM. The structures of the compounds were elucidated by spectroscopical methods.