Studies toward the Total Synthesis of Parvifolals A/B: An Intramolecular -Quinone Methide [4 + 2]-Cycloaddition To Construct the Central Tetracyclic Core.

Two different approaches funded upon the intramolecular [4 + 2]-cycloaddition of in situ generated -quinone methides have been explored to construct the central tetracyclic core of parvifolals A/B. At the outset, a cross-pinacol coupling of 2-formyl tri--methyl resveratrol with 4-methoxysalicylaldehyde followed by acid treatment was found to provide the desired tetracyclic core with an internal olefin. The requisite pendant aryl group has been introduced by a Pd-catalyzed direct coupling of corresponding diazonium salt.