Used in bioorthogonal and labeling chemistry for rapid and selective conjugation in biological systems due to the high ring strain of the bicyclo[1.1.1]pentane core and the reactivity of the isothiocyanate group with nucleophiles such as amines. Enables protein labeling via lysine residues, live-cell imaging, and construction of complex biomolecular architectures with minimal interference in native biochemical processes. Also applied in drug discovery for creating covalent inhibitors targeting nucleophilic residues and linking payloads in targeted therapeutics. Its compact, rigid structure serves as a bioisostere for phenyl rings, improving pharmacokinetic properties when incorporated into small molecules.