N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-D-glutamic acid (Fmoc-D-Glu-OH) is used in peptide synthesis as a protected building block for incorporating D-glutamic acid. The Fmoc group protects the α-amino function, enabling selective coupling via the α-carboxyl group in solid-phase peptide synthesis (SPPS) while preventing unwanted side reactions. The side chain carboxyl remains unprotected, suitable for applications requiring a free γ-carboxyl. The Fmoc group is easily removed under mild basic conditions (e.g., piperidine in DMF), facilitating stepwise peptide chain assembly. It is widely employed in the synthesis of complex peptides, proteins, pharmaceutical compounds, and bioactive peptides, particularly in research and drug discovery. Its stability and compatibility with various solvents make it a versatile reagent in organic and medicinal chemistry.