Two amino acids join together under the right conditions to form a dipetide. If we react glycine (gly) with alanine (ala) a mixture of 4 products is obtained: gly-ala, ala-gly, gly-gly and ala-ala.

To exclusively obtain the gly-ala dipeptide, it is necessary to protect the amino group of glycine and the acid group of alanine. In this way, the reaction will take place exclusively between the acid group of glycine and the amino group of alanine.

The protection of the amino and acid groups makes it possible to selectively obtain the gly-ala dipeptide.