This specialized linker is utilized in advanced peptide synthesis, featuring a fluorenylmethyl ester (Fm ester) protecting group on one terminal carboxylic acid. The structure consists of the Fm-protected carbonyl linked via an amide to an 2-aza-octakis(ethyleneoxy) chain (equivalent to NH-(CH₂CH₂O)₈-CH₂COOH), providing a hydrophilic PEG8 spacer with a free distal carboxylic acid. It is employed in solid-phase peptide synthesis (SPPS) to introduce soluble PEG linkers, enhancing peptide solubility, stability, and biocompatibility. The Fm group offers excellent stability under basic coupling conditions and selective removal under mild acidic conditions, facilitating precise assembly of complex PEGylated peptides, proteins, and bioconjugates for pharmaceutical and biotechnological applications.