Asymmetric synthesis of both enantiomers of anti-4,4,4-trifluorothreonine and 2-amino-4,4,4-trifluorobutanoic acid

A short and efficient enantioselective synthesis of both enantiomers of anti-4,4,4-trifluorothreonine and 2-amino-4,4,4-trifluorobutanoic acid was successfully developed. Trifluoromethylation of benzyl-protected bromoalkene 4 provided key intermediate trifluoromethylated transdisubstituted alkene 2 in good yield. The sequence then involved Sharpless asymmetric dihydroxylation, nucleophilic opening of cyclic sulfate with NaN3, palladium-catalyzed selective hydrogenation, and oxidation.