Bucherer-Bergs condensation

Several hydrolytic enzymes other than esterases have been applied for synthetic purposes. One important subject is the chemoenzymatic preparation of amino acids. An industrial method for the synthesis of unnatural d- or L-amino acids employs the enzymatic hydrolysis of hydantoins, prepared by Bucherer-Bergs condensation using either D- or L-hydantoinase (cf Section 3.2.1.4) [33]. Another efficient method of preparing natural and unnatural amino acids is the two-step synthesis which features a Pd-catalyzed amidocarbonylation (eq. (2) cf Section 2.1.2.4) to afford racemic A-acyl amino acids followed by enantioselective hydrolysis using various acylases [34]. 

The enzyme, Af-carbamoyl o-amino acid amidohydrolase can be incorporated with hydantoinase to produce o-amino acids in one step from the corresponding racemic hydantoins. Because many of the five-substituted hydantoins undergo spontaneous racemization under the enzymatic reaction conditions (pH > 8), complete conversion from racemic hydantoin to the o-amino acid can be achieved. The starting hydantoins are prepared by the Bucherer-Bergs reaction (Scheme 9.34), the simple condensation of potassium cyanide and ammonium carbonate with the... 

The Strecker [1] and Bucherer-Bergs [2] reactions are the most important strategies and powerful tools for the synthesis of a-amino acids from a carbonyl compound and cyanide. The classical first approach uses ammonium hydroxide and potassium cyanide to obtain the corresponding aminonitrile compound 1, whereas the second one is a four-component condensation between an aldehyde or ketone derivative reacting with potassium cyanide and ammonium carbonate as source of ammonia and carbon dioxide affording hydan-toin componnds 2 [3], In both cases, final hydrolysis would deliver the corresponding o,a-disubstituted a-amino acid derivatives 3 (Scheme 10.1) [4],... 

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