Synthesis of benzofuranoid systems. IV. Total synthesis of cyperaquinone and conicaquinone

Abstract

The total synthesis of the novel naturally occurring benzodifuroquinones, cyperaquinone (1) and conicaquinone (2), starting from phloroglucinol is described. A comparison of synthetic and natural compounds confirmed the original structural assignments. The key intermediate in the synthesis was the 3-methylbenzofuran (21) which was prepared in high yield by an internal site-specific base-catalysed Ar₁-5 cyclization of the acetonyloxy derivative (19). The method has also been applied to the syntheses of linear furocoumarins and dibenzofurans.