Thalidomide 4'-ether-PEG2-azide is a click chemistry modified cereblon (CRBN) inhibitor Thalidomide. Thalidomide 4'-ether-PEG2-azide contains an azide group and can undergo copper-catalyzed azide-alkyne cycloaddition reaction (CuAAc) with molecules containing alkynyl groups. Thalidomide 4'-ether-PEG2-azide can be used as a ligand of E3 ubiquitin ligase and Linker conjugates (E3 Ligase Ligand-Linker Conjugates) for the synthesis of PROTACs[1].