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New Synthesis and Chirality of (−)-4,4,4,4′,4′,4′-Hexafluorovaline

✍ Scribed by Marcel K. Eberle; Reinhart Keese; Helen Stoeckli-Evans

Publisher
John Wiley and Sons
Year
1998
Tongue
German
Weight
267 KB
Volume
81
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

(−)‐(R)‐4,4,4,4′,4′,4′‐Hexafluorovaline hydrochloride ((R)‐5) of 98% ee is prepared from β,β‐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.

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