Copper-Catalyzed Direct Asymmetric Aldol Reaction of Glycine Schiff Bases to Access <i>syn</i>-β-Hydroxy-α-amino Esters

This study reported a copper-catalyzed direct asymmetric aldol reaction between aldehydes and glycine Schiff bases with methyl, allyl, and <i>tert</i>-butyl esters. Additionally, this reaction afforded high yields of <i>syn</i>-β-hydroxy-α-amino esters with excellent enantio- and diastereoselectivities (93-99% ee, up to >99:1 dr). The aldol reaction accepted aromatic, linear aliphatic, and α-substituted aliphatic aldehydes.