Structure Revision of the Fungal Phytotoxin Cavoxin and of Its Corresponding Chroman-4-one Cavoxone by X-ray Crystallography.

Cavoxin ( 1 ) was isolated as the main phytotoxin produced by Phoma cava Schulzer, a toxigenic fungus isolated from Castanea spp. Its structure was determined by 1D NMR and MS in 1985 along with that of the corresponding chroman-4-one cavoxone ( 2 ), an artifact formed by acid treatment of 1 . Since that time cavoxin was shown to be phytotoxic, antifungal, antifeedant, herbicidal, and antirust with potential application in agriculture and medicine. During a study aimed at improving cavoxin's production by P. cava , single crystals for X-ray diffractometric analysis were obtained. The X-ray crystallography characterization confirmed only in part the structure proposed for cavoxin ( 1 ), revealing a different substitution pattern on the aromatic ring, as depicted in the revised structure 3 .