UUN06815, also known as (S,R,S)-AHPC-PEG4-Azide, is a ProTAC building block. This conjugate contains a von Hippel-Lindau (VHL)-recruiting ligand, a linker with both hydrophobic and hydrophilic moieties, and a pendant azide for click chemistry with an alkyne on the target ligand. When used with other protein degrader building blocks with a pendant azide group, parallel synthesis can be used to more quickly generate ProTAC libraries that feature variation in crosslinker length, composition, and E3 ligase ligand. This product has no formal name at the moment.