This compound, 3-((((9H-Fluoren-9-yl)methoxy)carbonyl)amino)-4-phenylbutanoic acid, is an Fmoc-protected derivative of 3-amino-4-phenylbutanoic acid (also known as β-homophenylalanine). It serves as a key building block in solid-phase peptide synthesis (SPPS), where the fluorenylmethoxycarbonyl (Fmoc) group protects the amino functionality during stepwise peptide chain assembly, preventing side reactions. The Fmoc protection is orthogonally removable under mild basic conditions (e.g., with piperidine), enabling precise incorporation of the non-natural amino acid residue into peptides. This specialty intermediate is widely used in the synthesis of complex peptides, peptidomimetics, pharmaceutical leads, and biochemical research tools, particularly for studying protein structure-function relationships or developing therapeutics.