Synthesis of the indoloazocine derivatives from a chiral indol amide-stabilized sulfur ylide

We present here a synthetic route for the access to a series of diverse indoloazocine derivatives through selective epoxidation of chiral sulfonium salt 4, which reacts with diverse aromatic and aliphatic aldehydes to give trans-glycidic amides, followed by an intramolecular electrophilic aromatic substitution promoted by Cu(OTf)2 giving the desired heterocyclic compound in a high chemical yield. Using this strategy, the total synthesis of (S,R)-(+)-norbalasubramide was achieved.