New Approach for Complete Reversal of Enantioselectivity Using a Single Chiral Source

尝试获得高对映体过量的两种对映体是有吸引力且重要的挑战，因为通常情况下每种对映体表现出不同的生物活性。本文综述了通过改变反应条件实现对映选择性完全逆转的方法。我们的新方法，以实现对映体选择性加成反应中的双乙烯酮醛提供光学活性的5-羟基-3-酮酯在高的光学产率使用含有恶唑啉部分衍生的L-丝氨酸的席夫碱，实现逆转的对映体选择性。从一个手性中心出发，得到了两个含恶唑啉基团的手性Schiff碱，它们在双乙烯酮与醛的加成反应中分别识别不同的醛对映体，并具有很高的识别率（分别高达93%ee R和89%ee（S））.这是从L-丝氨酸的单一手性完全逆转对映选择的第一个例子。

Attempt for obtaining both enantiomers in high enantiomeric excess is attractive and important challenges, because it is often the case that each enantiomer exhibits different bioactivity. This review summarizes some approaches to realize complete reversal of enantioselectivity by changing various conditions. Our new approach to achieve reversal of enantioselection in the reaction of enantioselective addition of diketene to aldehydes affording optically active 5-hydroxy-3-ketoesters in high optical yield using Schiff bases containing oxazoline moiety derived from L-serine, was achieved. Starting from one chiral center (in this case from L-serine), we obtained two chiral Schiff base possessing oxazoline moieties, each of which recognized different enantioface of aldehydes in the addition reaction of diketene to aldehydes in high level (up to 93% ee R and 89% ee (S), respectively). This is the first example of complete reversal of enantioselection from the single chirality of L-serine.