Used in bioconjugation processes to link biomolecules via click chemistry, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC). The azide group reacts selectively with alkynes, enabling efficient and modular assembly of complex biological constructs. The PEG5 spacer enhances water solubility and provides flexibility, reducing steric hindrance between conjugated components. Commonly applied in labeling peptides, proteins, and nucleic acids for imaging, diagnostics, and drug delivery. The tosyl group can act as a leaving group, allowing further functionalization or attachment to nucleophiles like amines or thiols. Useful in developing bioactive probes, PEGylated therapeutics, and multifunctional ligands in medicinal chemistry.