Thalidomide-NH-C10-Boc (compound S20) serves as a conjugate that combines the E3 ubiquitinase ligand Thalidomide with a PROTAC Linker, enabling the recruitment of Cereblon ubiquitinase. This compound facilitates the coupling of target protein ligands via the PROTAC Linker to create PROTAC molecules capable of inducing degradation. An instance of its function includes the coupling with EP300/CBP ligand 2 to form the PROTAC molecule dCE-2.