Synthesis of Functionalized Pyroglutamic Acids, Part 1. The Synthetic Utility of N-Acylindole and the Ugi Reaction with a Chiral Levulinic Acid

A variety of pyroglutamic acid derivatives are readily synthesized via N-acylindole intermediates obtained by the Ugi reaction. For the preparation of functionalized pyroglutamic acid derivatives, the diastereoselectivity of the Ugi 4-center 3-component condensation reaction with a chiral γ-keto acid and convertible isocyanide is described.