CbzNH-PEG4-CH2COOH is a PEG linker containing an carboxylic acid (CO2H) group and a benzyl (Cbz) protecting group. The hydrophilic PEG spacer increases the water solubility of a compound in aqueous media. The terminal carboxylic acid is reactive with primary amine groups in the presence of activators (e.g. EDC, or HATU) forming a stable amide bond. The benzyl protecting group can be removed via hydrogenolysis to form a free amine.
