Stereocontrolled synthesis of β-hydroxyphenylalanine and β-hydroxytyrosine derivatives

Abstract

Side-chain bromination of N-phthaloyl-(S)-phenylalanine and tyrosine derivatives, followed by treatment of the product bromides with silver nitrate in aqueous acetone, affords the corresponding (2S,3R)-β-hydroxy-α-amino acids, enantiospecifically and diastereoselectively. The diastereoselectivity depends on the carboxyl protecting group. tert-Butyl esters display greater stereoselectivity than the corresponding methyl esters, presumably as a result of a steric effect, while N-tert-butylamides react diastereospecifically due to a combination of steric and electronic effects. © 1994.