Commercial Preparation of Unnatural Amino Acids by Deracemization

Period of Performance: 08/01/2007 - 01/31/2008


Phase 1 SBIR

Recipient Firm

Richmond Chemical Corporation
Oak Brook, IL 60523
Principal Investigator


DESCRIPTION (provided by applicant): Unnatural amino acids represent one of the largest classes of intermediates used by the pharmaceutical, agrochemical and fine chemical industries. Demand for these compounds at large- scale and high optical purity is now very significant, due to their application in single enantiomer pharmaceuticals, particularly for the areas of virology and oncology. No synthetic or biosynthetic method however, has proven sufficiently versatile to prepare these compounds broadly at scale. Richmond Chemical Corporation has recently developed an efficient and general chemo-enzymatic process to prepare enantiomerically pure L- and D- amino acids in high yield by deracemization of racemic starting materials. This method involves the concerted action of an enantioselective amino acid oxidase biocatalyst and a non-selective chemical reducing catalyst to effect the stereo-inversion of one enantiomer and can result in an enantiomeric excess of > 99 % from the starting racemate, with product yields of over 90 %. This approach, conducted entirely in water, (thereby minimizing waste streams) compares very favorably to resolution processes which have a maximum single pass yield of 50 %. We have successfully developed methods to optimize the efficiency of the process and establish competitive economics at scale. However, the current breadth of application of this process is limited by the substrate range of the oxidase biocatalysts. We now propose to apply powerful methods of in vitro enzyme evolution to demonstrate the adaptability of the biocatalysts, and therefore the general process, to prepare many unnatural amino acids required for pharmaceutical development. These amino acids are of high relevance due to their favorable pharmacokinetic properties but are difficult to prepare by traditional methods. As a result, our approach offers significant advantages to the fine chemical and life sciences industries by reducing costs, processing requirements and waste disposal. In Phase I, amino acid oxidases with high activity and enantioselectivity towards sterically bulky amino acids will be isolated through in vitro evolution of our current process biocatalysts. In Phase II we will develop the scalable chemo-enzymatic deracemization processes to prepare these unnatural amino acids and optimize critical reaction parameters including substrate load, biocatalyst production, formulation and re-use, as well as product isolation and recovery. The results of the laboratory evolution work will enable us to adapt the oxidase biocatalysts to many further targets. In Phase III the optimized deracemization processes will be implemented in the commercial manufacture of unnatural amino acids at large-scale. This work plan will result in new general bioprocess technology for the fine chemical industry, to produce chiral synthetic intermediates, agrochemicals and pharmaceuticals at commercial scale. This project is aimed towards the development of an economical enzymatic process for the synthesis of optically pure unnatural amino acids. These amino acids are in great demand for the synthesis of a wide range of important pharmaceutical compounds such HIV protease inhibitors, anti-cancer agents and anti-diabetic drugs.