This compound, Fmoc-N-methyl-PEG3-CH2CH2COOH, is widely used in peptide synthesis, particularly for the introduction of polyethylene glycol (PEG) spacers with an N-methyl linkage. The Fmoc group serves as a protecting group for the N-methyl amine during solid-phase peptide synthesis, ensuring precise control over the assembly of peptide chains. The PEG3 spacer enhances solubility and stability of the peptide, while also reducing immunogenicity, making it valuable in the development of therapeutic peptides and bioconjugates. The carboxylic acid end group allows for further conjugation to other molecules, such as targeting ligands or drugs, enabling the creation of multifunctional constructs for drug delivery systems. Its application is particularly relevant in the design of peptide-based drugs, where improved pharmacokinetics and targeted delivery are critical.