Synthesis of Pyranocyclopentaindolines Representing the Western Sections of Janthitrem B, JBIR‐137, and Shearinine G

摘要

Abstract The synthesis of the ABCD tetracyclic partial structures of the fungal indole diterpenes janthitrem B, JBIR‐137, and shearinine G is reported. The route starts from 5‐formylated indoline that is coupled to a dihydropyran moiety, followed by Prins cyclization. A diene was obtained that was oxygenated in a divergent manner. The hydroxylated tetracyclic western half of janthitrem B was obtained in eight steps and 10  overall yield. We also share our experience with alternative approaches passing via alkynylated precursors. This includes the gold‐catalyzed cycloisomerization of a 6‐ethynyl‐5‐prenylindoline.