Metabolites of pathogenic fungi. VII. On the structure and stereochemistry of xanthomegnin, vioxanthin, and viopurpurin, pigments from Trichophyton violaceum

Abstract

Recently, we proposed structure 1 for xanthomegnin (1) and tentatively assigned structures 2 and 3 for vioxanthin and viopurpurin respectively (2). We should now like to present evidence which confirms the structure of vioxanthin (2), adds weight to the structure proposed for viopurpurin, and which defines the stereochemistry of the lactone ring in 1 and 3.