Asymmetric protonation of lithium enolate of alpha-amino acid derivatives using chiral Bronsted acids

Chiral alcohols possessing an asymmetric 2-oxazoline ring were synthesized as new chiral Bronsted acids from tetrahydro-2-furoic acid and (IS, 2R)-2-a mino-1,2-diphenylethanol. These alcohols were superior to (S,S)- or (R,R)-i mide reported previously as a chiral proton source for enantioselective pro tonation of lithium enolate of,in alanine derivative.