Regioselective and stereoselective nucleophilic ring opening of trifluoromethylated cyclic sulfates: asymmetric synthesis of both enantiomers of syn-(3-trifluoromethyl)isoserine.

A novel and efficient enantioselective synthesis of both enantiomers of syn-(3-trifluoromethyl)isoserine was achieved. Ring opening of trifluoromethylated cyclic sulfates 3, derived from enantiopure trifluoromethylated vicinal diols 2, with various nucleophiles occurred exclusively at C2 with inversion of chirality. Treatment of 4c and 4d, obtained by nucleophilic opening of 3a and 3b with PhCO2NH4, with (CF3SO2)2O followed by substitution with sodium azide, Jones oxidation, and hydrogenolysis furnished (2S,3S)-(N-benzoyl)-3-(trifluoromethyl)isoserine 9a and (2R,3R)-(N-benzoyl)-3-(trifluoromethyl)isoserine 9b, respectively.