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- Title
Asymmetric Synthesis of ( S)-5,5,5,5′,5′,5′,5′-Hexafluoroleucine.
- Authors
Zhang, Cong; Ludin, Christian; Eberle, Marcel K.; Stoeckli-Evans, Helen; Keese, Reinhart
- Abstract
( S)-5,5,5,5′,5′,5′-Hexafluoroleucine (( S)- 13) of 81 % ee is prepared from hexafluoroacetone ( l) and ethyl bromopyruvate (= ethyl 2-oxopropanoate) in 7 steps with an overall yield of 18% ( Schemes 1 and 2). Key step in this sequence is the highly enantioselective reduction of the carbonyl group in α-keto ester 4 either by bakers' yeast (91 % ee) or by 'catecholborane' 6 utilizing an oxazaborolidine catalyst, yielding hydroxy ester ( R)- 5 with 99% ee. The absolute configuration was determined by X-ray analysis of the HCl adduct ( S,R)- 9b of (2 S)- N-[( R)- l-phenylethyl]-5,5,5,5′,5′,5′-hexafluoroleucine ethyl ester.
- Publication
Helvetica Chimica Acta, 1998, Vol 81, Issue 1, p174
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19980810116