Boc-C1-PEG3-C4-OBn (PROTAC Linker 15) is a PEG-based PROTAC linker employed in the synthesis of various PROTACs, including PROTAC SGK3 degrader-1. PROTACs are composed of two distinct ligands connected by a linker; one ligand binds to an E3 ubiquitin ligase, while the other specifically interacts with the target protein. By leveraging the intracellular ubiquitin-proteasome system, PROTACs can selectively degrade target proteins[1].