Pentafulvene for the synthesis of complex natural products: total syntheses of (±)-pallambins A and B

Abstract

The first total syntheses of pallambins A and B are enabled by the use of pentafulvene in an unprecedented Diels-Alder reaction. After elaboration of the adduct through chemoselective cyclopropanation, strategic CH insertion affords the dense tetracyclic core of the natural products. 1,3-Dipolar cycloaddition and palladium(II)-catalyzed alkoxycarbonylation were leveraged for the construction of the hexacyclic scaffold en route to both natural products.

Keywords: CH insertion; cycloaddition; natural products; small-ring systems; total synthesis.