Boc-Aminooxy-PEG4-Tos（Cat No.:I014721）is a multifunctional polyethylene glycol linker featuring a Boc-protected aminooxy group at one end and a tosyl (Tos) leaving group at the other, connected via a four-unit PEG chain. The Boc group temporarily protects the aminooxy functionality, enabling controlled deprotection for selective oxime or hydrazone ligation with aldehydes and ketones. The tosyl group provides a reactive handle for nucleophilic substitution, allowing versatile functionalization. The PEG4 backbone improves solubility, flexibility, and reduces steric hindrance. This reagent is widely applied in peptide chemistry, bioconjugation, and drug discovery for multifunctional molecule construction.