Cyanide will react with iminium ions to form α amino nitriles. Although these compounds are relatively unimportant in their own right, a simple hydrolysis step produces α amino acids. This route to amino acids is known as the Strecker synthesis. Of course, it’s not usually necessary to make the amino acids that Nature produces for us in living systems: they can be extracted from hydrolysed proteins. This Strecker synthesis is of phenylglycine, an amino acid not found in proteins. Cyanide reacts more rapidly with the iminium ion generated in the fi rst step than it does with the starting benzaldehyde.

This compound is the toxin used by the orb weaver spider to paralyse its prey. Notice that it has a guanidine at its right-hand end. These are stable imines, and their powerful basicity was discussed in Chapter 8.

Since the spider produces only minute quantities of the compound, chemists at the University of Bath set about synthesizing it in the laboratory so that they could study its biological properties. The toxin contains several amide and amine functional groups, and the chemists decided that the best way to make it was to link two molecules together at one of the secondary amine groups using a reductive amination.

The compound made by this reaction has almost, but not exactly, the spider toxin structure. The extra groups in brown are protecting groups that prevent unwanted side-reactions at the other amine and phenol functional groups. We will discuss protecting groups in detail in Chapter 23.

مواضيع ذات صلة

Lithium aluminium hydride reduces amides to amines

Iminium ions can react as electrophilic intermediates

Secondary amines react with carbonyl compounds to form enamines

Iminium ions and oxonium ions

Some imines are stable

Imines are usually unstable and are easily hydrolysed

Imines are the nitrogen analogues of carbonyl compounds

Amines react with carbonyl compounds

Modifying reactivity using acetals

Cyclic acetals are more stable than acyclic acetals

Acetals hydrolyse only in the presence of acid

Amines from imines: reductive amination