Stereoselective reduction of N-hydroxy-α-iminocarbonyl-oligopeptide methyl esters with Zn–MsOH

The reduction of N-hydroxy-α-imino esters with Zn–MsOH in THF afforded α-amino esters in high yields. The reduction of N-hydroxy-α-iminocarbonyl-oligopeptide methyl esters prepared from l-phenylalanine and l-leucine di-, tri-, tetrapeptides gave the corresponding S-formed oligopeptide methyl esters in moderate diastereoselectivities.