Two new phytotoxins, vasinfectins A and B, were isolated from the phytopathogenic fungus Neocosmospora vasinfecta NHL2298. Their structures, diastereomers of each other, were determined to be (E)-2-(3-hydroxy-2,4-dimethyl-1-hexenyl)-2,7-dimethyl-5-propanoyl-2H-benzo[b ]furan-3-one by 2D NMR. The absolute stereochemistry of C-10 and C-11 in these vasinfectins was established by chemical reactions.