Widely used in medicinal chemistry as a protected amine building block for drug design, particularly in the development of bioisosteres. The bicyclo[1.1.1]pentane core serves as a rigid, three-dimensional spacer that can replace traditional phenyl or alkyne groups, improving pharmacokinetic properties such as metabolic stability and solubility. The tert-butyloxycarbonyl (Boc) protecting group allows for controlled deprotection under mild acidic conditions, enabling stepwise synthesis in complex molecule assembly. Commonly employed in the preparation of CNS-targeted therapeutics and proteolysis-targeting chimeras (PROTACs) due to its favorable physicochemical properties and ability to enhance blood-brain barrier penetration. Also used in fragment-based drug discovery to introduce high sp3 character and reduce planarity, which can lead to improved selectivity and reduced off-target effects.