Used in peptide and protein synthesis to introduce a PEGylated spacer with an amine handle for further conjugation. The Fmoc group allows for solid-phase synthesis by providing temporary protection, while the triethylene glycol (PEG3) linker enhances solubility and flexibility. The terminal primary amine, as the hydrochloride salt, is ideal for coupling with carboxylic acids or other electrophiles to attach labels, tags, or functional molecules. Commonly applied in the development of bioconjugates, drug delivery systems, and functionalized peptides where improved pharmacokinetics and reduced aggregation are desired.