Synthesis of the altertoxin III framework

The framework of altertoxin III, a mycotoxin produced by Alternaria fungi investing food and feed, has been synthesised for the first time. Synthetic schemes including Diels–Alder reactions of anthracene derivatives turned out to be not successful due to an aromatisation of key intermediates. This aromatisation was further investigated by DFT calculations, which showed that the aromatisation tendency is dependant from the electronic characteristics of attached substituents. A Friedel–Crafts-type hafnium triflate-catalysed dimerisation of dihydroxytetralins with subsequent benzylic oxidation furnished the target compound, which should be a suitable precursor for the synthesis of altertoxin III and related natural products.