The Dakin-West Reaction of N-Alkoxycarbonyl-N-alkyl-α-amino Acids Employing Trifluoroacetic Anhydride

Abstract

The Dakin-West reaction of N-alkoxycarbonyl-N-alkyl-α-amino acids (1a-j) with trifluoroacetic anhydride in the presence of pyridine gave α-amido trifluoromethyl ketones (2a-j), in which probable intermediates were mesoionic 1, 3-oxazolium-5-olates (munchnones). The diastereoselective reduction of 2a-f with NaBH₄ gave the threo-aminoalcohols (5a-f), which may be explained by the Felkin-Anh model. This was confirmed by converting 5a-f into trans-5-trifluoromethyl-2-oxazolidinones (6a-f) in good yields.