Quinone epoxides. V.1 The biosynthesis of terreic acid

Abstract

Tracer studies using the 14C-labeled salts of acetic acid, 6-methylsalicylic acid, and orsellinic acid demonstrate that the carbon skeleton of terreic acid (3,4-epoxy-6-hydroxy-2,5-toluquinone), a metabolite of Aspergillus terreus, is biosynthesized by the acetate–malonate pathway and that 6-methylsalicylic acid is an intermediate in this process. Orsellinic acid does not appear to be involved. Molecular 18O is incorporated into the metabolite, and distinction can be made between incorporation at the epoxide oxygen and the three remaining oxygens on the basis of exchange rates. By this method the epoxide oxygen is shown to originate from atmospheric oxygen. The overall biosynthetic pathway is discussed.