Preparation of Enantiomerically Pure beta,beta-Diaryl beta-Hydroxy-alpha-Amino Acids and Evaluation of Their Potential as Organocatalysts

摘要

A general synthetic procedure was developed for enantiomerically pure beta,beta-diaryl beta-hydroxy-alpha-amino acids 5, starting from readily available oxazolidine ester 1 and a wide variety of Grignard reagents. The problematic oxidative decomposition of beta-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 beta,beta-diaryl beta-hydroxy-alpha-amino acids 5 was evaluated with respect to asymmetric fluorination of 2-phenylpropionaldehyde 6, and moderate enantioselectivity, 61%, was achieved using compound 5 f.