Enzymatic Syntheses of a-Amino Acids

Enzymatic methods have a long history and wide applicability both in lab-scale and in industrial synthesis of a-amino acids [21, 22, 26, 27]. These transformations can be grouped into two classes A) enzymatic resolution of racemic amino acid derivatives [21,22,27], and B) asymmetric bond-forming reactions [21, 27, 92]. A comprehensive discussion of enzymatic syntheses of amino acids is well beyond the scope of this chapter, but a few selected examples are briefly presented to illustrate the importance of such transformations. As shown below, typical examples of enzymes that effect resolution include aminopeptidases (Equation 12) [93], nitrilases (Equation 13) [94], acylases (Equation 14) [95], esterases (Equation 15) [96], and oxidases (Equation 16) [97]. 

Two examples of enzymatic systems that mediate bond-formation reactions are the aminotransferases (Equation 17) [98] and the lyases (Equation 18) [99] these show great promise for development of the field. Generally, enzymatic synthesis can offer significant advantages, such as ease of execution and the isolation of products with high optical purity. Indeed, any chemical method that is intended for use on process scale must compare favorably with the high standard set by enzymatic methods. 

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