Phomalone, an antifungal metabolite of Phoma etheridgei

Abstract

The metabolites produced by liquid cultures of Phoma etheridgei, a new fungus isolated from black galls of aspen, have been examined. This fungus is antagonistic to the aspen decay fungus Phellinus tremulae. The compound responsible for this antagonism has been isolated and its structure elucidated. Phomalone (1) is a previously undescribed natural product that possesses the same carbon skeleton as the Phoma pigmentivora metabolite LL-D253α. The structure was determined by physical methods, mainly 1H and 13C NMR. INAPT experiments played an important role. Some chemical transformations of phomalone (1) are described and it is shown by 13C-labelling experiments to be derived from six acetate units. Phomalone is active against Phellinus tremulae. Compounds 4, 6, 7, and 8 are also new natural products produced by P. etheridgei.