2-Azido-PEG3-amido-13-biscarboxylethoxypropane is a PEG-based PROTACs linker that can be used in the synthesis of PROTACss. 2-(Azido-PEG3-amido)-1,3-bis(carboxylethoxy)propane 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.