Eupenifeldin is a bistropolone metabolite isolated from Eupenicillium brefeldianum by researchers at Bristol-Myers Squibb in 1993 as an antitumor agent. Its structure was solved by crystallography to reveal a central 11-membered macrocycle flanked by two dihydropyrans coupled to tropolones. More recently, eupenifeldin was isolated from a strain of Phoma in good yields. Eupenifeldin is a very potent antitumor agent with activity at the nanogram level in in vitro tumor cell lines and has weak nematocidal activity against the free living stages of the sheep parasitic nematode, Haemonchus contortus.