An Efficient Chemoenzymatic Approach to (S)-gamma-Fluoroleucine Ethyl Ester

摘要

An asymmetric synthesis of (S)-gamma-fluoroleucine ethyl ester 1 is described.The key transformation involves a lipase-catalyzed dynamic ring-opening of 2-(3-butenyl)azlactone 7b with EtOH to give amide ester (S)-6b in 84% enantiomeric excess.Removal of the N-pentenoyl group with N,N'-dibro-modimethylhydantoin in the presence of trifluoroacetic acid afforded the titled compound,which was isolated as its hydrogen sulfate salt in 75% yield and >97% ee.