The biosynthesis of phenols. Part XV. Some metabolites of Penicillium citrinum related to citrinin

Seven compounds related in structure to citrinin (I) have been isolated from cultures of Penicillium citrinum. This, taken with previous evidence from carbon-14 labelling studies and the isolation of dihydrocitrinone (IV) from a blocked mutant of Aspergillus terreus allows proposals concerning the pathway of biosynthesis of citrinin to be made. In vitro conversion of dihydrocitrinone into citrinin is described. The formation of 5-(2-formyloxy-1-methylpropyl)-4-methylresorcinol (XII), through retro-aldol cleavage of citrinin, is discussed.