Which of these reactions are used to make amino-acids

Question

BlackTom AI · Accepted Answer

To evaluate which reactions are used to make amino acids, I will go option by option and connect each to known synthetic routes for amino acids.
Option: formation of an imine from an aldehyde. In the classic Strecker synthesis of amino acids, an aldehyde reacts with ammonia (or an amine) to form an imine (or iminium ion). This imine formation is the initial step that sets up the carbon-nitrogen framework needed for subsequent addition of a nucleophile. So this step is indeed used in amino-acid synthesis via Strecker chemistry.
Option: addition of phthalidmide to 2-bromomalonic ester. This describes a key step in the Gabriel synthesis of amino acids, where phthalimide is introduced to create an N-phthalimidomethyl malonate equivalent, which after hydrolysis yields an amino acid. Therefore, this reaction is used for amino-acid synthesis.
Option: addition of a nitrile to an imine. In the Strecker sequence, after forming the imine from an aldehyde, cyanide (a nitrile anion equivalent) adds to the imine to form an α-aminonitrile intermediate. This addition step is central to producing the amino group-bearing carbon skeleton that becomes an amino acid after hydrolysis. Thus, this reaction is used.
Option: hydrolysis of a nitrile. The Strecker pathway ends by hydrolyzing the nitrile to a carboxylic acid, yielding the amino acid in its classic form (the amino function is already in place from the earlier steps). Hence, nitrile hydrolysis is a needed step in amino-acid synthesis via this route.
Option: hydrolysis of phthalimide and malonic ester. This is the workup step in the Gabriel synthesis: after forming the phthalimide-derived intermediate, hydrolysis and decarboxylation release the free amino acid. Therefore, this hydrolysis is indeed used in amino-acid synthesis via the Gabriel route.
Option: all of these. When we consider the Strecker route (imine formation, nitrile addition, nitrile hydrolysis) and the Gabriel route (phthalimide malonate formation, its subsequent hydrolysis to the amino acid), every listed reaction contributes to established methods for making amino acids. 
Option: none of these. Given the connections identified above, this option is incorrect because multiple listed reactions are indeed involved in amino-acid synthesis.
In summary, each of the first five options corresponds to a step in well-known amino-acid synthesis strategies (Strecker and Gabriel), and therefore they collectively support the statement that all of these are used in amino-acid synthesis. The "none of these" choice is inconsistent with these established methods.

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