Deracemization of Amino Acids

描述（由申请人提供）：非天然氨基酸（UAA）正日益成为重要的药物中间体，应用于许多当前和未来的药物。由于UAA几乎总是需要作为纯的立体异构体，因此手性合成优于最常用的拆分方法。在阶段I中，证明了制备L-对映异构体的单锅去外消旋化工艺。在该方法中，使用D-氨基酸氧化酶将D，L-氨基酸混合物的D-对映体选择性氧化为相应的2-酮酸。然后通过L-氨基酸转氨酶或L-氨基酸脱氢酶将2-酮酸立体选择性胺化为L-氨基酸。这是在一个反应步骤中完成的，中间体不需要分离，也不需要保护基团或衍生化。产率和对映体过量值接近100%。该方法具有广泛的范围，将适用于各种UAA产品。定向进化被用于许多研究的酶，以产生更有活性的酶突变体。在第二阶段，将进一步确定和优化去消旋化过程。将对许多酶进行定向进化，以产生具有增强的活性和更广泛的底物特异性的突变体。此外，将研究氨基酸的去外消旋化以制备纯D-对映体。将以100 g规模证明用于制备纯L-或D-对映异构体的两种方法用于重要的商业目标。

DESCRIPTION (provided by applicant): Unnatural amino acids (UAAs) are increasingly becoming important pharmaceutical intermediates, with applications in a number of current and future drugs. Since UAAs are almost always required as pure stereoisomers, a chiral synthesis is preferred over the resolution methods that are most commonly employed. In Phase I the single-pot deracemization process to make the L-enantiomer was demonstrated. In this method the D-enantiomer of a D,L-amino acid mixture is selectively oxidized to the corresponding 2- ketoacid using a D-amino acid oxidase. The 2-ketoacid is then stereoselectively aminated to the L-amino acid by an L-amino acid transaminase or an L-amino acid dehydrogenase. This is accomplished in a reaction single step, intermediates need not be isolated nor is it necessary for protecting groups or derivatization. Yields and enantiomeric excess values approach 100 percent. This method has a broad scope and will be applicable to a wide range of UAA products. Directed evolution was used on a number of the enzymes investigated to create more active enzyme mutants. In Phase II the deracemization process will be further characterized and optimized. Directed evolution will be performed on a number of the enzymes to create mutants with enhanced activity and broader substrate specificity. In addition, the deracemization of amino acids to make the pure D-enantiomer will be investigated. Both methods, for making the pure L- or D-enantiomer will be demonstrated on the 100 gram scale for important commercial targets.