Used in peptide synthesis as a protecting group for amino acids, ensuring selective reactions during the formation of peptide bonds. The PNP (para-nitrophenyl) ester facilitates efficient coupling reactions, while the PAB (para-aminobenzyl) group enhances stability and controlled release. Commonly applied in the development of therapeutic peptides and complex biomolecules, it aids in the precise construction of peptide chains. Its design allows for easy deprotection, making it valuable in solid-phase peptide synthesis and drug discovery processes.