New synthesis and chirality of (-)-4,4,4,4′,4′,4′-hexafluorovaline

(-)-(R)-4,4,4,4',4',4'-Hexafluorovaline hydrochloride ((R)-5) of 98% ee is prepared from beta,beta-bis(trifluoromethyl)acrylic acid (= benzyl 4,4,4-trifluoro-3-(trifluoromethyl)but-2-enoate; 1) in 4 steps with an overall yield of 9.6%. Key step is the separation of the TsOH salts of the diastereoisomers obtained by anti-Michael addition of (+)-(R)-1-phenylethylamine (2) to 1 (--> (R,R)-3). In contrast to the published (S)-chirality, the X-ray structure analysis of (R,S)-6 reveals, that (R)-chirality has to be assigned to the levorotatory (-)-4,4,4,4',4',4'-hexafluorovaline hydrochloride.