The Dakin-West reaction of N-alkoxycarbonyl-N-alkyl-alpha-amino acids employing trifluoroacetic anhydride

The Dakin-West reaction of N-alkoxycarbonyl-N-alkyl-alpha-amino acids (1a-j ) with trifluoroacetic anhydride in the presence of pyridine gave alpha-ami do trifluoromethyl ketones (2a-j), in which probable intermediates were mes oionic 1,3-oxazolium-5-olates (munchnones), The diastereoselective reductio n of 2a-f with NaBH4 gave the threo-aminoalcohols (5a-f), which may be expl ained by the Felkin-Anh model, This was confirmed by converting 5a-f into t rans-5-trifluoromethyl-2-oxazolidinones (6a-f) in good yields.