Synthesis of the Altertoxin I Framework

Routes to the framework of perylenequinone-derived mycotoxins of the biphenyl type are described. 1,2,11,12-Tetrahydroperylenequinone is most suitably prepared in seven steps starting with 3-hydroxyacetophenone. Key steps are an Ullmann coupling, pinacol-type cyclization, bromination, enolate reaction, and intramolecular Friedel-Crafts cyclization. A second approach starting with 1,5-dihydroxynaphthalene yields the respective decarbonylated core. Key steps of this 5-step sequence are again an Ullmann coupling and a McMurry olefination. The cleavage of the preferentially utilized hexyl protecting group could be achieved with boron bromide.