Strecker amino-acid synthesis

The Strecker synthesis is a name reaction in organic chemistry. Their discoverer, Adolph Strecker (1822-1871), she published the first time in 1850. It is a special case of the Mannich reaction, arise in the of aldehydes, ammonia and potassium cyanide ( KCN) α - amino carboxylic acids or amino acids. The synthesis is further applicable to primary and secondary amines.

Mechanism

The reaction proceeds by the nucleophilic addition of ammonia to aldehydes, it extends generally to the imine. At this also electrophilic species, the cyanide is added, it is created as an α - amino nitrile ( a nitrile with an amino group ), which can be hydrolyzed under acidic conditions to α -amino acid.

Practice

Disadvantage of the Strecker synthesis is mainly that due to the lack of asymmetric induction, the amino acids arise racemic. This increases due to the per se reduced to 50% yield and subsequent costly separation processes, in general, the kinetic resolution, the cost considerably. Similarly, the use of cyanide due to its toxicity is problematic. Some Strecker synthesis, however, have prevailed in the large-scale technical production, since the starting materials ( especially ammonia and hydrogen cyanide ) are partly very inexpensive and there are still focused on these Synthesenweg old plants. The Bucherer -Bergs reaction is, for example, a variant used.

There are also asymmetric Strecker synthesis. In the variant of Kunz et al. used is a chiral 1- amino sugar ( β -D -galactosamine ) instead of ammonia, the asymmetric induction is sufficient to achieve a satisfactory enantiomeric excess.

Another interesting approach to the asymmetric version of the Strecker synthesis was developed by the research group Enders. You are using SAMP - hydrazones as asymmetric induction in the addition of cyanide.