作者:Cong Zhang、Christian Ludin、Marcel K. Eberle、Helen Stoeckli-Evans、Reinhart Keese
DOI:10.1002/hlca.19980810116
日期:1998.1.12
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 (2S)-N-[(R)- l-phenylethyl]-5,5,5,5′,5′,5′-hexafluoroleucine
(S)-5,5,5,5,5',5',5'-六氟丙酮(l)和溴丙酮酸乙酯(= 2-氧代丙酸乙酯)制备81%ee的六氟亮氨酸((S)-13)步骤总产率为18%(方案1和2)。在这个序列中的关键步骤是羰基的α-酮酯的高度对映选择性还原4或者通过面包酵母(91%ee)或非由‘儿茶酚’ 6利用恶唑硼烷催化剂,得到羟基酯([R )- 5与99%ee。通过X射线分析HCl加合物(S,R)-9b确定绝对构型(2 S)-N -[(R)-1-苯乙基] -5,5,5,5',5',5'-六氟亮氨酸乙酯的衍生物。