Chamilactones A and B, Sesquiterpenes from the Endophytic Fungus Chaetomium nigricolor F5

A bioassay-guided chemical investigation of the endophytic fungus Chaetomium nigricolor F5 resulted in the discovery of two novel sesquiterpenes, chamilactones A and B (1 and 2), with a new 9,10-seco-15-nor-isoilludalane carbon skeleton, together with several biosynthetically related precursors (3–8). Their structures and absolute configurations were elucidated by the analysis of MS, NMR, calculated 13C chemical shifts, ECD calculations, and single-crystal X-ray diffraction data. It was proposed that an unprecedented carbon–carbon bond cleavage between C-9 and C-10 in 3–8 was the key step in the biosynthetic pathway of 1 and 2. Compound 3 displayed potent neuroprotective effects by reducing the phosphorylation level of p65 and inhibiting its nuclear translocation in the TLR4-mediated NF-κB signaling pathway in LPS-induced BV2 microglial cells.