Total Synthesis of Exiguamines A and B Inspired by Catecholamine Chemistry

AbstractThe evolution of a total synthesis of the exiguamines, two structurally unusual natural products that are highly active inhibitors of indolamine‐2,3‐dioxygenase (IDO), is described. The ultimately successful strategy involves advanced cross‐coupling methodology and features a potentially biosynthetic tautomerization/electrocyclization cascade reaction that forms two heterocycles and installs a quaternary ammonium ion in a single synthetic operation.