m-PEG5-Boc is a PEG-based PROTAC linker can be used in the synthesis of PROTACs[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[1].
[1]. Balasingam Radhakrishnan, et al. Fatty acid formulations for oral delivery of proteins and peptides, and uses thereof. US20060018874A1.