Efficient regiospecific synthesis of two cytotoxic furonaphthoquinones, 5,7-dimethoxy-4,9-dihydronaphtho[2,3-b]furan-4,9-dione and 5,6,7-trimethoxy-4,9-dihydronaphtho[2,3-b]furan-4,9-dione

Abstract

Following the recent isolation of several furonaphthoquinones from two Latana species (Verbenaceae), a novel synthetic method for the preparation of two cytotoxic furonaphthoquinones, 5,7-dimethoxy-4,9-dihydronaphtho[2,3-b]furan-4,9-dione 8a and 5,6,7-trimethoxy-4,9-dihydronaphtho[2,3-b]furan-4,9-dione 8b is described. The title compounds were obtained in high overall yield via hydrogen peroxide oxidation of intermediate 4-hydroxy-9-trifluoroacetylnaphthofurans. Both the title compounds exhibit cytotoxic activity towards three mammalian cell lines (2.99–6.6 µmol dm^–3).