Addition of 2-Lithiofuran to Chiral α-Alkoxy Nitrones; a Stereoselective Approach to α-Epimeric β-Alkoxy-α-amino Acids

Abstract

The addition of 2-lithiofuran (1) to the N-benzyl nitrones 2a-d, derived from chiral α-alkoxy aldehydes, affords β-alkoxy-α-hydroxyamino-2-alkylfurans in good yields and with syn selectivity. Conversely, the reaction with the same nitrones precomplexed with diethylaluminum chloride leads to the same adducts but with anti selectivity. Three pairs of epimeric hydroxylamines are subjected to reductive N-dehydroxylation with titanium(III) chloride and then to furyl-carboxylic acid conversion with ruthenium tetroxide to give the corresponding α-epimeric β-alkoxy-α-amino acids.