Biocatalytic Synthesis of Chiral N-Functionalized Amino Acids.

N-Functionalized amino acids are important building blocks for the preparation of diverse bioactive molecules, including peptides. The development of sustainable manufacturing routes to chiral N-alkylated amino acids remains a significant challenge in the pharmaceutical and fine-chemical industries. Herein we report the discovery of a structurally diverse panel of biocatalysts which catalyze the asymmetric synthesis of N-alkyl amino acids through the reductive coupling of ketones and amines. Reactions have been performed on a gram scale to yield optically pure N-alkyl-functionalized products in high yields.

N-Alkyl-α-amino acids in Nature and their biocatalytic preparation.

N-Alkylated-α-amino acids are useful building blocks for the pharmaceutical and fine chemical industries. Enantioselective methods of N-alkylated-α-amino acid synthesis are therefore highly valuable and widely investigated. While there are a variety of chemical methods for their synthesis, they often employ stoichiometric quantities of hazardous reagents such as pyrophoric metal hydrides or genotoxic alkylating agents, whereas biocatalytic routes can provide a greener and cleaner alternative to existing methods. This review highlights the occurrence of the N-alkyl-α-amino acid motif and its role in nature, important applications towards human health and biocatalytic methods of preparation. Several enzyme classes that can be used to access chiral N-alkylated-α-amino acids and their substrate selectivities are detailed.