Four New Cytotoxic Arborinane-Type Triterpenes from the Endolichenic Fungus Myrothecium inundatum.

Two new arborinane-type triterpenes, myrotheols A (1: ) and B (2: ), two new arborinane-type glycosides, myrothesides C (3: ) and D (4: ), together with four known diterpenes (5:  - 8: ) were isolated from the ethyl acetate extract of the endolichenic fungus Myrothecium inundatum. The structures of new compounds 1:  - 4: were elucidated by NMR and MS analyses. The absolute configuration of 1: was assigned by a single-crystal X-ray diffraction experiment. Compounds 3: and 4: represent the first two natural 4-O-methyl-α-D-mannosides. Compounds 1:  - 8: exhibited cytotoxicity against K562 and RKO human cancer cell lines. Georg Thieme Verlag KG Stuttgart · New York.