Millmerranones A-F: A Meroterpene Cyclic Carbonate and Related Metabolites from the Australian Fungus Aspergillus sp. CMB-MRF324

A brown rice cultivation of Aspergillus sp. CMB-MRF324 yielded six new meroterpenes, millmerranones A-F (1-6), and four known analogues, terreulactones A-D (7-10). Millmerranone A (1) possesses a unique carbon skeleton bearing a rare cyclic carbonate and undergoes an unprecedented base mediated rearrangement to seco-millmerranone A (1a). We also report on an unexpected base rearrangement of 7 to 7a/b; a plausible biosynthetic relationship linking 1, 7, and 9; and acetylcholinesterase inhibitory properties (IC₅₀ 37 nM to >30 μM).