Preparation of Enantiomerically Pure β,β‐Diaryl β‐Hydroxy‐α‐Amino Acids and Evaluation of Their Potential as Organocatalysts

A general synthetic procedure was developed for enantiomerically pure β,β‐diaryl β‐hydroxy‐α‐amino acids 5 , starting from readily available oxazolidine ester 1 and a wide variety of Grignard reagents. The problematic oxidative decomposition of β‐aminodiols 3 , due to their instability in the presence of metallic oxidants, was successfully suppressed using Parikh‐Doering oxidation and subsequent Pinnick oxidation. Additionally, the organocatalytic ability of β,β‐diaryl β‐hydroxy‐α‐amino acids 5 was evaluated with respect to asymmetric fluorination of 2‐phenylpropionaldehyde 6 , and moderate enantioselectivity, 61%, was achieved using compound 5 f .