Question

Show how the following amino acids might be formed in the laboratory by reductive amination of the appropriate $\alpha$-ketoacid.

Phenylalanine (b) Cysteine (c) Serine (d) Alanine

Short answer

(a)

Formation of phenylalanine

(b)

Formation of cysteine

(c)

Formation of serine

(d)

Formation of alanine

Step-by-step solution

Reductive amination

The amination that involves the reduction of a carbonyl group to an amine group via the formation of an intermediate amine is referred to as reductive amination.

Reaction of ketoacid with ammonia

(a)

The reductive amination of an $\alpha$ketoacid to form phenylalanine is as shown below:

Formation of phenylalanine

(b)

The reductive amination of an $\alpha$ketoacid to form cysteine is as shown below:

Formation of cysteine

(c)

The reductive amination of an $\alpha$ketoacid to form serine is as shown below:

(d)

The reductive amination of an $\alpha$ketoacid to form alanine is as shown below:

Formation of alanine