NH2-C4-NH-Boc (compound 15) is a PROTAC linker, which refers to the Alkyl/ether composition. NH2-C4-NH-Boc can be used in the synthesis of a series of PROTACs. PROTACs contain two different ligands connected by a linker; one is a ligand for an E3 ubiquitin ligase and the other is for the target protein. PROTACs exploit the intracellular ubiquitin-proteasome system to selectively degrade target proteins[1].