Synthesis of azanzone A, a new naturally occurring o-naphthoquinone

Abstract

The synthesis is reported of 7-hydroxy-5-isopropyl-3,8-dimethylnaphthalene-1,2-dione 2 which was found to be identical with the natural product azanzone A, thus confirming the structure of the latter. The synthesis was achieved using the Stobbe condensation to obtain the butanedioic acid mono-ester 8 which readily cyclised to give the naphthoate 9. Reduction of the ester to a methyl group, followed by Fremy's salt oxidation and O-demethylation with boron tribromide completed the synthesis.