Oxabicyclic Building Blocks as Key Intermediates in the Synthesis of the Natural Products (−)-Platensimycin and (+)-Frondosin A

Abstract For over 10 years, our research group has been interested in the application of an older but underutilized reaction, the direct cycloaddition of furans and perhalocyclopropenes, for the synthesis of polycyclic natural products and their analogs. This high-complexity-building reaction proceeds through an initial Diels–Alder reaction followed by a spontaneous rearrangement to yield an oxabicyclo[3.2.1]octadiene system with ample functionality for further synthetic elaboration. We have worked to make this reaction a central feature in the synthesis of a variety of natural product targets. Herein, we detail the asymmetric syntheses of two terpenoid natural products, platensimycin and frondosin A, where this formal cycloaddition process was employed to prepare an integral cycloheptane ring system embedded in the polycyclic frameworks.