Flavipesines A and B and Asperchalasines E-H: Cytochalasans and Merocytochalasans from Aspergillus flavipes.

Flavipesines A and B (1 and 2) and asperchalasines E-H (3-6), two cytochalasans with an unusual ring system and four merocytochalasans possessing a 5/6/11/5/5/6 ring system, were isolated from Aspergillus flavipes, along with three related compounds (7-9). Their structures, including absolute configurations, were determined on the basis of data from HRESIMS, NMR, ECD, molecular modeling, and single-crystal X-ray diffraction. Flavipesines A and B (1 and 2) represent the first examples of cytochalasans possessing a 5/6/7/6 ring system with a C-18-O-C-21 bridge. Compounds 3, 7, and 9 show moderate inhibitory activities against isocitrate dehydrogenase 1 (IDH1). This is the first report on the IDH1 inhibitory activities of cytochalasans.