Amichalasines F-J: cytochalasan heterotrimers with mirror-imaged core structures from Aspergillus micronesiensis

Amichalasines F-J (1-5), five new cytochalasan heterotrimers composed of two aspochalasins and one epicoccine unit, along with asperchalasine A (6), were isolated from Aspergillus micronesiensis. Their structures, including absolute configurations, were elucidated using extensive spectroscopic data, quantum chemical calculations, and single X-ray diffraction analyses. Compound 1 possesses a different fusion pattern between the aspochalasin and epicoccine unit compared with 6, resulting in a mirror-imaged epicoccine unit. Interestingly, compounds 2-4 also possess mirror-imaged core structures of 6, even though they have the same fusion pattern. Compounds 1, and 2-4 represent two new kinds of cytochalasan heterotrimers. Plausible biosynthetic pathways of 1-6 are proposed. Compounds 2-4 exhibited potent cytotoxic activities against six human cancer cell lines, and the IC50 values against HL60 ranged from 4.36 to 5.69 mu M.