Protein degrader builiding block Pomalidomide-PEG6-NH2 (HCl salt) enables the synthesis of molecules for targeted protein degradation and PROTAC (proteolysis-targeting chimeras) technology. This conjugate contains a Cereblon (CRBN)-recruiting ligand and a PEGylated crosslinker with pendant amine for reactivity with a carboxyl group on the target ligand. Because even slight alterations in ligands and crosslinkers can affect ternary complex formation between the target, E3 ligase, and PROTAC, many analogs are prepared to screen for optimal target degradation. When used with other protein degrader building blocks with a pendant amine, parallel synthesis can be used to more quickly generate PROTAC libraries that feature variation in crosslinker length, composition, and E3 ligase ligand.