Non‐Enzymatic Hybrid Catalysis for Stereoconversion of l ‐Amino Acid Derivatives to d ‐Isomers

A catalytic transformation of N ‐unprotected l ‐amino esters to N ‐protected d ‐amino esters was developed. The combined use of a heteroaromatic aldehyde, Lewis acid, palladium complex, and chiral Brønsted acid was a key factor for the successful operation of this catalytic system. The synergistic cooperation of an appropriate aldehyde and Lewis acid was crucial for promoting an efficient racemization of l ‐amino esters, while the combination of a palladium complex and chiral phosphoric acid enabled dynamic kinetic resolution through asymmetric N‐allylation, providing N ‐protected d ‐amino esters in good yields with up to 97 : 3 er. Following appropriate deprotection processes, d ‐amino acids were obtained without loss of enantiomeric purity.