endo-BCN-PEG2-PFP ester is a PEG-based PROTAC linker that can be used in the synthesis of PROTACs[1]. endo-BCN-PEG2-PFP ester is a click chemistry reagent, it contains a BCN group that can undergo strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing Azide groups.