A Genomic Approach to New Methods in Asymmetric Synthesis - Revised

官能化烯烃的不对称还原提供了丰富多样的手性结构单元。与醛、酮、酯或硝基共轭的烯烃的金属催化的不对称氢化通常是有问题的。烯烃还原酶为不对称烯烃还原提供了一种有用的新合成方法。通过改造这些酶以进行随后的立体选择性硝基羟醛（亨利）反应，可以显著增加它们的合成效用。已知在NADPH存在下催化烯酮还原的旧黄色酶将是开发酶作为活化烯烃还原的立体选择性催化剂的另一个起点。将在序列数据库中克隆和表达31个已知和推定的烯烃还原酶基因。所得蛋白质将针对一组官能化烯烃的底物选择性和立体选择性进行表征，提供关于每种蛋白质的有用范围的第一信息，特别是关于可接受的烯烃活化基团（共轭酮或醛、酯、酸、腈、硝基）。蛋白质工程将允许硝基烯烃还原之后进行亨利缩合。最后，烯烃还原酶（野生型和工程变体）将被应用于从简单的非手性起始材料不对称合成β-2-氨基酸以及α-羟基-β-氨基酸和β-羟基-γ-氨基酸。佛罗里达大学化学系的斯图尔特说。斯图尔特教授和他的学生正在开发方法来适应和利用酶的催化能力，招募他们的能力，进行选择性和有效的反应。酶催化剂可以被修饰以作用于非天然底物，允许向现有活性位点添加新的催化功能。该项目预计将提供多种酶催化剂，易于储存和易于用于有机合成，以及促进快速建立分子复杂性的催化剂。碳-碳键的形成是有机合成的基石，生物催化策略将大大增加可用于构建这些键的工具库。

Asymmetric reductions of functionalized alkenes provide a rich variety of chiral building blocks. Metal-catalyzed asymmetric hydrogenations of olefins conjugated with aldehydes, ketones, esters or nitro groups are generally problematic. Alkene reductase enzymes offer a useful, new synthetic method for asymmetric olefin reductions. By engineering these enzymes to carry out a subsequent stereoselective nitro aldol (Henry) reaction, their synthetic utility can be increased dramatically. Old yellow enzyme, known to catalyze enone reduction in the presence of NADPH, will be an additional starting point for the development of enzymes as stereoselective catalysts for activated alkene reductions. Thirty-one known and putative alkene reductase genes in the sequence database will be cloned and expressed. The resulting proteins will be characterized with respect to substrate- and stereoselectivities toward a set of functionalized alkenes, providing the first information on the useful range of each protein, particularly with respect to the acceptable alkene activating group (conjugated ketone or aldehyde, ester, acid, nitrile, nitro group). Protein engineering will allow nitroalkene reduction to be followed by a Henry condensation. Finally, alkene reductases (both wild-type and engineered variants) will be applied to the asymmetric synthesis of beta-2-amino acids as well as alpha-hydroxy-beta-amino acids and beta-hydroxy-gamma-amino acids from simple, achiral starting materials.With this award, the Organic and Macromolecular Chemistry Program is supporting the research of Professor Jon D. Stewart, of the Department of Chemistry at the University of Florida. Professor Stewart and his students are developing methods to adapt and exploit the catalytic capability of enzymes, recruiting their ability to carry out selective and efficient reactions. Enzyme catalysts may be modified to act on non-natural substrates, allowing the addition of new catalytic functions to an existing active site. The project is expected to provide a diverse collection of enzyme catalysts, easily stored and easily employed for organic synthesis, as well as catalysts that facilitate rapid establishment of molecular complexity. Carbon-carbon bond formation is a cornerstone of organic synthesis, and biocatalytic strategies will add appreciably to the arsenal of tools available for the construction of these bonds.