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. ? ?
| Lepesheva, Galina I; Hargrove, Tatiana Y; Rachakonda, Girish et al. (2015) VFV as a New Effective CYP51 Structure-Derived Drug Candidate for Chagas Disease and Visceral Leishmaniasis. J Infect Dis 212:1439-48 |
