Used in bioconjugation and pharmaceutical research to link molecules with controlled spacing and stability. The azide group enables click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), allowing efficient attachment to alkynes. PEG1 spacer provides water solubility and flexibility, while the Boc-protected amine allows for selective deprotection and further functionalization. Commonly applied in the development of antibody-drug conjugates (ADCs), peptide modifications, and surface immobilization of biomolecules. Its short polyethylene glycol chain minimizes steric hindrance without compromising solubility.