A C–H Activation Approach to the Tricyclic Core of Glionitrin A and B

[Image: see text] Synthesis of diketopiperazines has been of long-standing interest in both natural product synthesis and medicinal chemistry. Here, we present an operationally convenient and efficient approach to the fused indoline-diketopiperazine tricyclic core of glionitrin A/B and related structures using a Pd-catalyzed C–H activation reaction to form the indoline five-membered ring. Exploratory work aimed at elaborating the tricyclic structures into the corresponding natural products is discussed.