New Bergamotane Sesquiterpenoids from the Plant Endophytic Fungus Paraconiothyrium brasiliense

Brasilamides K-N (1-4), four new bergamotane sesquiterpenoids; with 4-oxatricyclo (3.3.1.0 (2,7))nonane (1)and 9-oxatricyclo(4.3.0.0 (4,7))nonane (2-4) skeletons; were isolated from the scale-up fermentation cultures of the plant endophytic fungus Paraconiothynium brasiliense Verkley. The previously identified sesquiterpenoids brasilamides A and C (5 and 6) were also reisolated in the current work. The structures of 1-4 were elucidated primarily by interpretation of NMR spectroscopic data. The absolute configurations of 1-3 were deduced by analogy to the co-isolated metabolites 5 and 6; whereas that of C-12 in 4 was assigned using the modified Mosher method. The cytotoxicity of all compounds against a panel of eight human tumor cell lines were assayed.