Sorbicillfurans A and B, two novel sorbicillinoid adducts from the fungus Penicillium citrinum SCSIO41402

Two novel sorbicillinoid adducts containing bicyclo[2.2.2] octane and tetrahydrofuran moieties, named sorbicillfurans A and B (1 and 2), were isolated from the static culture of the marine-derived fungus Penicillium citrinum SCSIO41402. Their structures including absolute configurations were determined by spectroscopic and calculated ECD analyses. Sorbicillfurans A and B (1 and 2) are the first examples of sorbicillinoids possessing a tetrahydrofuran unit. In the proposed biosynthetic pathway, sorbicillfuran B (2), harboring a rare and complex polycyclic framework, is probably formed by two Diels-Alder reactions. Both isolates were evaluated for the cytotoxicity against six human cancer cell lines, only sorbicillfuran B (2) showed weak cytotoxicity against HL-60 cells with an IC50 value of 9.6 mu M.