Asymmetric Synthesis of α,α-Difluoro-β-amino Acid Derivatives from Enantiomerically Pure N-tert-Butylsulfinimines

Addition of the Reformatsky reagent derived from ethyl bromodifluoroacetate to alkyl- and aryl-substituted N-tert-butylsulfinimines furnishes β-tert-butylsulfinamyl-β-substituted α,α-difluoroproponiates in diastereomeric ratios ranging from 80:20 to 95:5. The diastereomers are easily separated and the enantiomerically pure, protected β-amino esters are readily transformed to the corresponding acid, amide, and amine derivatives as useful synthons for medicinal chemistry targets.