The Direct Catalytic Enantioselective Synthesis of Protected Aryl β‐Hydroxy‐α‐Amino Acids

The combination of three reagents—a tridentate pybox ligand (pybox=pyridine bis(oxazoline)), magnesium perchlorate, and Hünig base (iPr2EtN)—allows the catalytic generation of a chiral glycine enolate from 1 that undergoes highly enantioselective addition to a range of aryl aldehydes 2. The protected aryl β-hydroxy-α-amino acid products obtained include a protected version of one of the aryl serine units present in the glycopeptide antibiotic vancomycin.