Used in peptide synthesis as a building block, particularly in solid-phase peptide synthesis (SPPS). It helps in the sequential addition of amino acids to create specific peptide sequences. The Fmoc group acts as a protecting group for the amine functionality, ensuring controlled and precise synthesis. The Cit (citrulline) and Phe (phenylalanine) residues contribute to the peptide's structure and function, often used in research for studying protein interactions or developing therapeutic peptides. The PAB (para-aminobenzoic acid) linker enhances stability and facilitates cleavage from the resin during synthesis. Commonly applied in drug discovery, biochemistry, and the development of peptide-based pharmaceuticals.