Synthesis of Multi-functional Chiral Molecules by Developing the Function of Biocatalysts

1.多官能团手性构筑块的高立体选择性合成采用四步层析的方法，从面包酵母无细胞提取液中分离纯化了一种对1-氯-2-己酮具有还原活性的还原酶。通过脂肪酶催化的酯交换反应实现了几种手性构筑基团的高对映体选择性动力学拆分。人工提高对映体选择性我们偶然发现少量有机溶剂会影响面包师酵母还原1-氯-2，4-烷二酮的对映体选择性。通过使用有机溶剂、缓蚀剂和热处理，可将6%ee提高到94%ee。在有机溶剂中脂肪酶催化的酯交换反应中，原位生成了酰基酶中间体。通过改变酰基供体，改变了酰基酶的结构，从而有望改变对映体的选择性。在30~-60ﾟC的不同温度下进行脂肪酶催化的酯交换反应，结果表明，随着温度的降低，对映体选择性增加。将1NE与1/T作图形成一条直线，根据理论公式计算出DELTADELTAH^；对映体选择性的起源动力学研究表明，结合步骤中的手性识别对映体选择性并不重要，但手性识别作用于过渡态。将立体电子理论应用于脂肪酶催化反应，并对模型反应进行了分子轨道计算。提出了一个使对映体选择性合理化的过渡态模型。

1. Highly Stereoselective Synthesis of Polyfunctional Chiral Building BlocksA reductase that shows reducing activity toward 1-chloro-2-hexanone was purified from bakers'yeast cell-free extract by means of chromatographic separations in 4 steps. Reductants with high optical purity were obtained.Highly enantioselcective kinetic resolutions of several chiral building blocks were accomplished by the lipase-catalyzed transesterifications.2. Artificial Improvement of the EnantioselectivityWe incidentally discovered that a small amount of organic solvent can affect the enantioselectivity in the bakers'yeast reduction of 1-chloro-2,4-alkanediones. By using organic solvent, inhibitor, and heat treatment, the 6% ee was increased up to 94% ee.In the lipase-catalyzed transesterification in organic solvent, the acyl-enzyme intermediate is in situ formed. By changing the acyl donor, the structure of the acyl-enzyme is also changed, which is expected to change the enantioselectivity. Examination of this concept to 2-substituted cyclopentenols resulted in the change of the E values.The lipase-catalyzed transesterifications were performed at various temperatures ranging from 30 to -60ﾟC.As a result, the enantioselectivity was increased with decrease of the temperature. Plot of 1nE against 1/T afforded a straight line, from which DELTADELTAH^<<double plus>> and DELTADELTAS^<<double plus>> values were calculated according to a theoretical equation.3. Origin of the EnantioselectivityKinetic study revealed that chiral recognition in the binding step is unimportant for the enantioselectivity but that chiral discrimination operates at the transition state. Stereoelectronic theory was applied to the lipase-catalyzed reaction and molecular orbital calculations were performed on a model reaction. A transition -state model to rationalize the enantioselectivity was proposed.