In this research it has been shown by incorporation experiments using synthetic, labelled precursors that the antibiotics ethisolide (1) and canadensolide (2) have closely related biosynthetic origins in the appropriately substituted citric acids derived from condensation of a fatty acid derived moiety with a TCA cycle acid (probably oxaloacetate). The most convincing evidence to date for this pathway comes from the efficient and specific incorporation by P. canaderse of alpha-n-hexylitaconic acid into canadensolide (2) and the related metabolites
