Calamene-Type Sesqui-, Mero-, and Bis-sesquiterpenoids from Cultures of sp., a Basidiomycete Collected in Africa.

New meroterpenoids bis-heimiomycins A-D (-) and heimiomycins D and E ( and ) were isolated from solid rice cultures of sp., while new calamene-type sesquiterpenoids heimiocalamene A () and B () were isolated from shake cultures, respectively. Structures of the metabolites were elucidated by 1D and 2D NMR in addition to HRESIMS data. While relative configurations were assigned by ROESY data, absolute configurations were derived from the structurally related, previously described calamenes, which we herein name heimiocalamenes C-E (-). A plausible biosynthetic pathway was proposed for -, with a radical reaction connecting their central -benzoquinone building block to calamene-sesquiterpenoids. Based on the assumption of a common biosynthesis, we reviewed the structure of the known nitrogen-containing derivative , calling the validity of the originally proposed structure into question. Subsequently, the structure of was revised by analysis of HMBC and ROESY NMR data. Only heimiomycin D () displayed cytotoxic effects against cell line KB3.1.