EFFICIENT SYNTHESIS OF (S)-METHYL HEXAFLUOROVALINATE

anti-Michael addition of (R)-(+)-1-phenylethylamine to methyl bis(trif luoromethyl)acrylate (1b) leads to a 52:48 mixture of the diastereomer ic adducts (S,R)- and (R,R)-3a. After addition of hydrochloric acid, t he diastereomeric salt (S,R)-3b crystallizes in a pure form to give, u pon hydrogenolysis, an enantiomerically pure hydrochloric adduct of ()-methyl hexafluorovalinate [(S)-4] to which the (S)-configuration was assigned. Treatment of (R,R)-3a with BBr3 gave hexafluorovaline [(R)- 5].