Question

Draw all the steps in the synthesis of each peptide from individual amino acids:

(a)Gly-Ala;

(b) Ile-Ala-Phe

Short answer

The synthesis of a peptide is done by protecting the amino group of one amino acid with Boc or Fmoc group and protecting the carboxyl group of another amino acid as an ester.

After this, it is treated with DCC and then, removal of both protecting groups is done.

Step-by-step solution

Synthesis of a peptide from amino acids

The synthesis of a peptide is done by protecting the amino group of one amino acid with Boc or Fmoc group and protecting the carboxyl group of another amino acid as an ester.

After this, it is treated with DCC and then, removal of both protecting groups is done.

Synthesis of Gly-Ala

In this reaction, protection of Gly is done as a Boc derivative, and protection of carboxy group in Ala as an ester is done. A and B products then form an amide bond with DCC. After this, it reacts with HBr and ${\mathrm{CH}}_3\mathrm{COOH}$to form Gly-Ala.

Synthesis of Ile-Ala-Phe

In this reaction, protection of Ile is done as a Boc derivative, and protection of carboxy group in Ala as an ester is done. A and B products then form an amide bond when treated with DCC. After this, it undergoes elimination using and Pd catalyst to form C.

The protection of the carboxyl group in Phe as an ester is done. Now, this ester is treated with C and DCC. The compound formed further reacts with HBr and forms Ile-Ala-Phe.