Used in bioconjugation for site-specific labeling of biomolecules, particularly in click chemistry applications. Its strained alkyne group (BCN) reacts rapidly and selectively with azides via copper-free click reactions, making it ideal for labeling proteins, antibodies, or nucleic acids in live cells without cytotoxic effects. The PEG2 spacer improves solubility and reduces steric hindrance, enhancing reaction efficiency. The Boc-amine group allows for further chemical modifications under mild deprotection conditions, enabling stepwise synthesis in complex molecular constructs. Commonly employed in the development of antibody-drug conjugates (ADCs), imaging probes, and targeted therapeutics.