Strecker Reaction :Synthesis of Amino Acids| Mechanism

The condensation reaction of ketone or aldehyde with an ammonia or primary amine and various alkali cyanides (e.g., hydrogen cyanide,  KCN, Na-CN) to afford the corresponding α-amino nitrile is known as the Strecker reaction.

  The most well-known use of the Strecker reaction, α-amino nitriles, is their hydrolysis under acidic or basic conditions to obtain α-amino acids (Strecker amino acid synthesis).

Features of Strecker Synthesis of Amino Acids:

  • Strecker multicomponent reactions were also known as Strecker synthesis alanine.
  • The Strecker synthesis reaction is a one-pot three-component coupling reaction called Strecker multicomponent reaction. Aldehydes and ketones will give a good yield. In preparation of amino acid by Strecker synthesis, ammonia, primary, or secondary amine can be used as amine substrate.
  • The HCN is exceptionally toxic, so various alkali cyanides are usually used (e.g., KCN, NaCN) in buffered aqueous media.
  • In Strecker amino acid synthesis, adding HCN to preformed aldimines and Ketimines (even iminium salts) or oximes and hydrazones leads to N-substituted α-amino nitriles. It is a concern for Strecker synthesis in green chemistry.
  • In Strecker reaction conditions, hydrolysis of α-amino nitriles gives α-amino acids, reduction with metal hydrides affords 1,2-diamines, while strong bases can deprotonate at the α-carbon (if R2 =H), and the resulting carbanion can be trapped with a variety of electrophiles (umpolung)
strecker amino acid synthesis | strecker synthesis | The Strecker Synthesis of Amino Acids
strecker synthesis |strecker amino acid synthesis |alanine preparation

Asymmetrical Strecker reactions can be conducted while optically active amines generate chiral imines, which give rise to enantio-enriched α-amino nitriles upon the addition of cyanide ions and using organ-catalysts or chiral metal catalysts.  

In Strecker asymmetric reaction, optically active amines generate chiral imines in the catalytic asymmetric Strecker reaction, which gives rise to enantio-enriched α-amino nitriles upon the addition of cyanide ions.  

Strecker Synthesis Mechanism:

strecker reaction mechanism| strecker synthesis mechanism |
Strecker reaction mechanism| Strecker synthesis mechanism

Synthetic Applications:

The asymmetric Strecker reaction was used to construct the key tetramethyltryptophan subunit.

Related Reaction of Strecker Synthesis:

  1. Essential Amino Acids List
  2. Asymmetric Strecker reaction
  3. Schmidt reaction

Reafferences :

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