Total Synthesis of Indoline-Based Natural Products and Their Analogues

We report a concise total synthesis strategy for accessing four fused tricyclic indoline-based natural products and their derivatives. The synthesis employs phosphine-catalyzed allylic alkylation as the key step to construct common precursors, which are subsequently functionalized to form the fused ring systems. Notably, the synthetic route is readily scalable, enabling the efficient preparation of a library of indoline-based alkaloids.