Thalidomide-O-C6-azide is a synthesized E3 ligase ligand-linker conjugate that incorporates the Thalidomide (HY-14658) based cereblon ligand and a linker used in PROTAC technology[1]. Thalidomide-O-C6-azide is a click chemistry reagent, it contains an Azide group and can undergo copper-catalyzed azide-alkyne cycloaddition reaction (CuAAc) with molecules containing Alkyne groups. It can also undergo strain-promoted alkyne-azide cycloaddition (SPAAC) reactions with molecules containing DBCO or BCN groups.