Synthesis of the cis-fused hexahydroxanthene system via cationic cascade cyclization

The cis-fused hexahydroxanthene system can be obtained through a cascade cyclization initiated by Lewis acid-mediated epoxide opening and terminated by reaction with a MOM-protected phenol. Only a single diastereomer of the product was obtained with stereochemistry verified by diffraction analysis. This demonstrates the viability of this approach to natural products containing the cis-fused hexahydroxanthene skeleton, and supports preparation of more complex targets through a similar strategy.