FIRST TOTAL SYNTHESIS OF PALMARUMYCIN C-6 BASED ON DOUBLE OXA-MICHAEL ADDITION OF 1,8-DIHYDROXYNAPHTHALENE TO 3-BROMO-1-INDENONE

摘要

Synthetic studies on palmarumycin C-6 with a naphthyl acetal at the C-3 position in 4,7-dihydroxy-1-indanone as a lower homologue of spirobisnaphthalenes are described herein. We investigated three approaches: 1) Nazarov cyclization of benzoylketene acetal, 2) intramolecular Friedel-Crafts acylation of naphtho[1,8-de]-1,3-dioxin-2-aryl-2-acetic acid chloride, and 3) double oxa-Michael addition of 1,8-dihydroxynaphthalene to 3-bromo-l-indenone. The last approach successfully afforded the natural product after the removal of acetates that serve as protecting groups for phenolic hydroxyls under acidic conditions.