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

Abstract

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 μM.