Synthesis, anticancer activity, and iron affinity of the Actinoplanes metabolite 7,8-dihydroxy-1-methylnaphtho[2,3-c]furan-4,9-dione

The first synthesis of 7,8-dihydroxy-1-methylnaphtho[2,3-c]furan-4,9-dione (1), an isofuranonaphthoquinone produced by an Actinoplanes strain is described. Lactone ring opening of 6-methylfuro[3,4-c]furan-1(3H)-one (4) with ortho-lithiated veratrole (3), oxidation of product alcohol 5, and Friedel-Crafts acylation of the resulting aroylcarboxylic acid 7 afforded the mono methyl ether 2 of the target compound. The latter was obtained by demethylation of 2 with BBr(3) in 14% overall yield. While mono ether 2 was distinctly more cytotoxic than catechol 1 against a panel of five Cancer cell lines, only the latter showed a siderophore-like binding affinity for Fe(III) with a complex dissociation constant K(D) of approximately 10(-29) M(3) (pM = 25.9).