Asymmetric synthesis of alpha-(heteroaryl)alkylamines and alpha -amino acids via nucleophilic 1,2-addition of lithiated heterocycles to aldehyde SAMP-hydrazones

The asymmetric synthesis of alpha-(heteroaryl)alkylamines was accomplished by employing a diastereoselective nucleophilic 1,2-addition of lithiated aromatic heterocycles to aldehyde SAMP-hydrazones, followed by BH_3 . THF or SmI_2 promoted removal of the chiral auxiliary. The CBz or benzoyl-protected amines were obtained in good yields (40%--78%) and excellent enantiomeric excesses (ee = 88%--99%). The methodology can be applied to the synthesis of highly enantioenriched alpha-amino acids (ee = 90%--99%).