m-PEG4-Boc is a cleavable 4-unit polyethylene glycol (PEG) linker, widely employed in the synthesis of antibody-drug conjugates (ADCs) [1]. Additionally, m-PEG4-Boc serves as a PEG-based PROTAC linker, enabling its utilization in the synthesis of PROTACs [2].

ADCs are comprised of an antibody to which is attached an ADC cytotoxin through an ADC linker[1]. PROTACs contain two different ligands connected by a linker; one is a ligand for an E3 ubiquitin ligase and the other is for the target protein. PROTACs exploit the intracellular ubiquitin-proteasome system to selectively degrade target proteins[2].