Isobenzofurans and ortho-benzoquinone monoketals in syntheses of xestoquinone and its 9- and 10-methoxy derivatives

Syntheses of (±)-xestoquinone, (±)-9-methoxyxestoquinone and (±)-10-methoxyxestoquinone are described. A convergent CD plus ABE plan using the appropriate isobenzofuran (CD) and naphthofuranone (ABE) has been implemented to provide these marine metabolites in overall yields of 18.3, 9.5 and 8.5%, respectively. The latter pair of compounds, previously evaluated as inhibitors of Topoisomerase II as an inseparable mixture, are now available separate and pure for the first time.