Fmoc-N-amido-dPEG8-acid is a monodisperse PEG product that is useful for peptide synthesis. The 28-atom dPEG spacer allows the introduction of a medium-length, hydrophilic spacer onto either end of a peptide chain or between two peptide chains. The flexible dPEG spacer conjugates to peptides using conventional peptide synthesis chemistry. Peptide PEGylation imparts water solubility to hydrophobic peptide chains. Also, PEGylated peptides have expanded hydrodynamic volumes, which can reduce or eliminate renal clearance, and are protected from proteolysis. The combination of decreased renal clearance and protection from proteolysis contributes to longer in vivo circulation times for PEGylated (as compared to non-PEGylated) peptides. Additionally, PEGylation diminishes a peptide′s antigenicity. This product is part of the Fmoc-N-amido-dPEGn-acid (n=2, 3, 4, 5, 6, 8, 12, 24, 36) product series. application： Fmoc-NH-PEG8-CH2CH2COOH is used in synthesis of protein-antiviral compound conjugates.