Biomimetic Total Syntheses of Callistrilones A, B, and D.

A biomimetic total syntheses of antibacterial natural products (±)-callistrilones A, B, and D, the first triketone-phloroglucinol-monoterpene hybrids with an unprecedented [1]benzofuro[2,3-a]xanthene and [1]benzofuro[3,2-b]xanthene pentacyclic ring system along with the postulated biosynthetic intermediate, isolated from the leaves of Callistemon rigidus, were achieved. The total synthesis features highly regio- and diastereoselective catalytic Friedel-Crafts alkylation, palladium-catalyzed Wacker-type oxidative cyclization, Michael addition, and late-stage diastereoselective epoxide formation from the extremely hindered β face as key steps.