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PALLADIUM-CATALYZED HYDROXYCYCLOPROPANOL RING-OPENING CARBONYLATIVE LACTONIZATION TO FUSED BICYCLIC LACTONES AND TOTAL SYNTHESIS OF PHLEGHENRINE ALKALOIDS
An original palladium-catalyzed ring opening carbonylative lactonization of synthetic available hydroxycyclopropanols was reported to efficiently synthesize tetrahydrofuran (THF) and tetrahydropyran (THP)-fused bicyclic γ-lactones, two unique scaffolds often found in quite a few natural products. This new developed reaction features mild reaction conditions, good functional group tolerability, and the scale-up abilities. The synthetic application was demonstrated in a short total synthesis of (±)-Paeonilide. The THF-fused bicyclic γ-lactone products can be readily diversified into some medicinally important structures, which further broadens the application of this new carbonylation approach.
The first total synthesis of Phleghenrine A was reported. This synthesis features an unprecedented inverse electron-demand Diels-Alder reaction and Tiffeneau-Demjanov ring expansion to rapidly construct bicyclo[3,2,2]-nonane core structure of Phleghenrine alkaloids. Two Diels-Alder adducts were synthesized, which were the synthetic precursors for divergent synthesis of Phleghenrine A and B, respectively.