Used as a key intermediate in the synthesis of proteolysis targeting chimeras (PROTACs), serving as an E3 ubiquitin ligase recruiter via cereblon modulation. The structure features an isoindoline-1,3-dione moiety substituted with a 2,6-dioxopiperidin-3-yl group for cereblon binding, linked at the 4-position to a flexible polyether (PEG-like) chain ending in a primary amine. This amine group facilitates conjugation to target protein-binding ligands, enabling the formation of bifunctional PROTACs that induce ubiquitin-mediated degradation of specific proteins. The polyether chain enhances water solubility, reduces non-specific protein binding, and provides linker flexibility to optimize degradation efficiency in biological systems. Widely applied in the development of targeted therapies for cancer and other diseases by selectively degrading oncogenic or disease-driving proteins.