Diketo-1,3-dioxin-2-ones underwent retro-Diels-Alder reaction on heating in toluene at 110 degrees C to generate alpha,gamma,epsilon-triketo-ketenes. These were trapped with alcohols to provide 2,4,6-triketocarboxylates, which were smoothly aromatized by sequential reaction with potassium carbonate and methanolic hydrogen chloride to give resorcylate esters. The reaction was applied in the total synthesis of the marine antifungal agents 15G256 beta (1), 15G256 iota (2), and 15G256 pi (3) and the mycotoxin S-(-)-zearalenone (4).