Phytoactive Eremophilanes Produced by the Weed Pathogen Drechslera gigantea

Phytoactive substances were present in a culture broth of Drechslera gigantea, a pathogenic fungus of several grasses. Twelve eremophilane sesquiterpenes (1, 2, 3, 4, 6, 7, 10, 11, 12, 13, 14, and 15) were isolated and structurally characterized by a combination of single-crystal X-ray diffraction and spectroscopic analyses. Most of these sesquiterpenoids were phytotoxic; however, compounds 1 and 3 caused chlorophyll retention, an activity previously associated with phytohormones.