N-α-(tert-Butoxycarbonyl)-N-ε-biotinyl-L-lysine is a specialized bifunctional chemical building block. It features a tert-butoxycarbonyl (Boc) protecting group on the α-amino group of L-lysine and a biotin moiety attached via an amide bond to the ε-amino group. This structure combines the orthogonal reactivity of a protected amine with the high-affinity binding capability of biotin to streptavidin/avidin. This compound is primarily used in chemical biology and proteomics research. Its main application is as a versatile linker or spacer for bioconjugation and affinity labeling. The Boc-protected amine allows for selective deprotection and further coupling to other molecules (e.g., peptides, drugs, or fluorophores), while the biotin tag enables efficient capture, purification, or detection of the resulting conjugate using streptavidin-based systems. It serves as a key intermediate in the synthesis of biotinylated peptides and probes for studying protein-protein interactions, cell surface labeling, and targeted delivery systems. The molecule is also relevant in the development of advanced therapeutic modalities. It can function as a component in the design of PROTACs (Proteolysis Targeting Chimeras) and other bifunctional degraders, where it may act as part of the linker connecting a target-binding ligand to an E3 ligase recruiter, leveraging biotin's properties for initial proof-of-concept studies or as a model system.