Asymmetric Synthesis of ( S )‐5,5,5,5′,5′,5′,5′‐Hexafluoroleucine | Zendy

Zhang Cong | Zendy; Ludin Christian | Zendy; Eberle Marcel K. | Zendy; StoeckliEvans Helen | Zendy; Keese Reinhart | Zendy

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Asymmetric Synthesis of ( S )‐5,5,5,5′,5′,5′,5′‐Hexafluoroleucine

Author(s) -

Zhang Cong,

Ludin Christian,

Eberle Marcel K.,

StoeckliEvans Helen,

Keese Reinhart

Publication year - 1998

Publication title -

helvetica chimica acta

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 0.74

H-Index - 82

eISSN - 1522-2675

pISSN - 0018-019X

DOI - 10.1002/hlca.19980810116

Subject(s) - chemistry , hexafluoroacetone , enantioselective synthesis , yield (engineering) , adduct , catalysis , yeast , absolute configuration , stereochemistry , ethyl ester , sequence (biology) , organic chemistry , biochemistry , materials science , metallurgy

( 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.

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