Thalidomide-O-PEG4-amine hydrochloride（Cat No.:I045291）is a functionalized thalidomide derivative featuring a polyethylene glycol (PEG4) linker terminated with an amine group, supplied as its hydrochloride salt for improved stability and handling. This bifunctional molecule is commonly used in the design of proteolysis-targeting chimeras (PROTACs) and other targeted protein degradation systems, where thalidomide serves as a cereblon (CRBN) ligand to recruit E3 ubiquitin ligase complexes. The PEG4 spacer enhances solubility, flexibility, and spatial orientation, facilitating optimal target engagement. It is a valuable intermediate for medicinal chemistry, chemical biology, and drug discovery applications.