Used in bioconjugation to link drugs, peptides, or proteins with targeting molecules or polymers. The Boc group protects the amine during synthesis and can be removed under mild acidic conditions to expose the amine for further reaction. The PEG spacer improves solubility, reduces aggregation, and enhances the stability of conjugated molecules. The terminal carboxylic acid allows coupling to amines via standard peptide coupling reagents like EDC/NHS. Commonly used in developing PEGylated therapeutics, antibody-drug conjugates (ADCs), and functionalized nanoparticles. Also applied in creating hydrogels and surface coatings where controlled bioactivity is needed.