Tetraglycine hydrochloride

Tetraglycine, or Gly-Gly-Gly-Gly, is an oligopeptide composed of four glycine monomers. It is used as a bifunctional linker with amino and carboxyl groups .

The terminal amino group can react with activated esters, carbonyl compounds, and carboxylic acids, e.g., in reductive amination reactions.

The terminal carboxyl group can react with primary amino groups in the presence of activators (carbodiimides or HATU), resulting in a stable amide bond.