Chiral synthesis of amino acid

Hydroxynitrile lyases (HNLs or oxynitrilases) catalyze C—C bond-forming reactions between an aldehyde or ketone and cyanide to form enantiopure cyanohydrins (Figure 1.15), which are versatile building blocks for the chiral synthesis of amino acids, hydroxy ketones, hydroxy acids, amines and so on [68], Screening of natural sources has led to the discovery of both... 

This section deals mainly with the metalation of lactim ethers and subsequent reaction with electrophiles to generate new C—C bonds at position 3 or 6. Hydrolysis of the products leads to new amino acid esters. The chief attraction of this synthetic route is the high degree of stereoselectivity in the carbon—carbon bond-forming step. It is known as the Schollkopf method for the chiral synthesis of amino acids. 

At the end of the reaction a keto acid has been converted to an amino acid, and the coenzyme pyridoxamine has been converted to the aldehyde pyridoxal. In enzymatic processes the reaction would then be run in the reverse direction with a different amino acid to regenerate the starting materials, and we found that that was also possible here. Thus this system is truly catalytic, converting a keto acid and a different amino acid into the new amino acid and new keto acid by running the process back and forth. The chiral synthesis of amino acids by this process, so closely related to that in an enzyme, may prove to be of practical interest. 

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