t-Boc-N-amido-PEG5-Tos is a PEG linker containing an amine group protected by tosyl (Tos) and tert-butyloxycarbonyl (Boc) groups, with the molecular formula C₂₂H₃₇NO₉S and a molecular weight of 491.60. Its structure consists of a pentavalent ethylene glycol (PEG5) spacer arm connecting the Boc protecting group and the Tos group. The hydrophilic PEG chain enhances water solubility, the Tos group serves as an excellent leaving group for nucleophilic substitution reactions, and the Boc group can be deprotected under mild acidic conditions to generate free amine. This reagent is prepared through organic synthesis, with a purity of ≥95%, and requires storage at low temperatures away from light. It is widely used in drug conjugation, biomolecular modification, and PROTAC molecule construction, serving as a key intermediate for linking functional molecules to carriers.