Total Synthesis of Stemarene and Betaerene Diterpenoids: Divergent Ring-Formation Strategy and Late-Stage C-H Functionalization (vol 4, pg 987, 2022)

A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed, and three of them were obtained for the first time via chemical synthesis. Starting from a common intermediate, two distinct tetracyclic frameworks containing diastereoisomeric bridged bicycles were constructed by a divergent ring reorganization strategy. Late-stage C-H functionalization through a xanthylation-oxygenation protocol furnished the corresponding oxygenated stereocenters or oxo functionality in high regio- and diastereoselective fashion within a complex hydrocarbon system. The stereochemical puzzles in (-)-2-acetoxybetaer- 13(17)-ene and (+)-7-acetoxybetaer-13(17)-ene were first predicted by the comparison of density functional theory (DFT)-nuclear magnetic resonance (NMR) data with the reported data and then unambiguously addressed through the total syntheses of natural products and three diastereomers. © 2022 Chinese Chemical Society. All right reserved.