Structural Biochemistry/Organic Chemistry/Synthesis

Synthesis

The synthesis of amino acids is vital to life itself. They are important because they are the basis of proteins and required for the synthesis of more complicated molecules such as vitamins. Amino acid synthesis is the process of creating amino acids from other molecules. Not all animals can synthesize all the amino acids. Non essential amino acids are those that are synthesized while the essential amino acids are those that need to be obtained through diet. Non-essential amino acids are the amino acids that can be synthesized in animals.

The amino acids synthesis pathways are grouped into six categories. They are grouped according to their similar mechanism or the use of similar enzymes to synthesize amino acids. These six categories are simple reactions, branch chain amino acids, aromatic amino acids, threonine/lysine, serine/glycine, and unique pathways.

Synthesis of Amino Acids

Hell-Volhard-Zelinsky

Using Hell-Volhard-Zelinsky Bromination, the creation of racemic alanine can be formed from propanoic acid. This can be done as Hell-Volhard-Zelinsky Bromination allows for an addition of a functional group at the carbon 2 of propanoic acid. Through this reaction, a nucleophile can displace the bromine that is formed on carbon number two. In using a nucleophile such as ammonia, the amino acid Alanine can therefore be formed. Due to the low yields produced by Hell-Volhard-Zelinsky Bromination, Gabriel Synthesis is preferred in the making of primary amines.

Mechanism of Hell-Volhard-Zelinsky Bromination:

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This reaction is followed by an addition of ammonia, which will displace bromine and form Alanine.

Gabriel Synthesis

The formed 2-substitued propanedioate can be alkylated, allowing for the preparation of a variety of substituted amino acids.

Mechanism of Gabriel Synthesis:

Gabriel synthesis mechanism

A propanedioate such as diethyl 2-bromomalonate would be used to form an amino acid such as Glycine. The difference however in the synthesis of Glycine from the Gabriel Synthesis from the regular Gabriel synthesis shown above, is that the group that is attached to the Nitrogen after the first step would be hydrolyzed to form two carboxylic acids. One of the carboxylic acid group would be then decarboxylated and hydrolysis would occur once again to cleave the imide group, which would result in the formation of Glycine.

Strecker Synthesis

This synthesis is based on the cyanohydrin formation that can occur from aldehydes and hydrogen cyanide. When this reaction is carried out in the presence of ammonia or ammonium cyanide with an acetaldehyde, formation of the amino acid Alanine can occur.

Mechanism of Strecker Synthesis of Alanine:

Strecker synthesis

Simple Reactions:The synthesis of Glutamine, Glutamate, Aspartate, Asparagines and Alanine

Glutamate is synthesized by the addition of ammonia to alpha-ketoglutarate.

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Synthesis of Glutamate

Using Glutamate, the addition of another ammonia molecule made Glutamine.

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Synthesis of Glutamine

Aspartate is made by the combination of Oxaloacetate and Glutamate.

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Synthesis of Aspartate

Asparagine can be made by adding ammonia directly to Aspartate.

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Synthesis of Asparagine

There are several methods for making Alanine. The most common way is the transferring of amine group from glutamate onto private.

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Synthesis of Alanine

References

Vollhardt, Peter (2010) Organic Chemistry Structure and Function Sixth Edition. ISBN:142920494X