S)-5.5,5,5',5',5'-Hexafluoroleucine ((S)-13) of 81 YO ee is prepared from hexafluoroacetone (1) and ethyl bromopyruvate (= ethyl 2-oxopropanoate) in 7 steps with an overall yield of 18% (Schemes f and 2). Key step in this sequence is the highly enantioselect~ve reduction of the carbonyl group in cc-keto ester 4 either by bakers' yeast (91 % ee) or by 'catecholborane' 6 utilizing an oxaraborolidine catalyst, yielding hydroxy ester (R)-5 with 99 %, ee. The absolute configuration was determined by X-ray analysis of the HC1 adduct (S,R)-9b of (2S)-N-[(R)-1 -phenyIethyl]-5,5,5,5',5',5'-hexafluoroleucine ethyl ester.

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( -)-(R)-4,4,4,4,4,4'-Hexafluorovaline hydrochloride ((R)-5) of 98 % ee is prepared from /l,/l-bis(trifluoromcthy1)acrylic acid (= benzyl 4,4,4-trifluoro-3-(trifluoromethyl)but-2-enoate; 1) in 4 steps with ail overall yield of 9.6%. Key step is the separation of the TsOH salts of the diastereoisomers obtained by unti-Michael addition of (+)-(R)-I-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'-hex~fluorova-line hydrochloride.