Toluene-4-sulfonic acid 2-(2-benzyloxycarbonylamino-ethoxy)-ethyl ester

2-(2-(((Benzyloxy)carbonyl)amino)ethoxy)ethyl 4-methylbenzenesulfonate is a PEG linker containing a tosyl group and benzyl (Cbz) protecting group. The hydrophilic PEG spacer increases the water solubility of a compound in aqueous media. The tosyl group is a very good leaving group for nucleophilic substitution reactions. The benzyl protecting group can be removed via hydrogenolysis to form a free amine.