Thalidomide-5-O-CH2-COOH is an E3 Ligase Ligand-Linker Conjugate consisting of Thalidomide (HY-14658) and NH-PEG3-NH-Boc. Thalidomide-5-O-CH2-COOH acts as a ligand for Cereblon to recruit CRBN protein. Thalidomide-5-O-CH2-COOH is a key intermediate in the synthesis of PROTAC molecules designed based on CRBN.