Fmoc-Asp(OtBu)-OH is widely used in peptide synthesis, particularly in solid-phase peptide synthesis (SPPS). It serves as a protected form of aspartic acid, where the Fmoc group protects the amino group, and the tert-butyl ester (OtBu) protects the carboxylic acid side chain. This protection ensures selective reactions during peptide chain assembly, preventing unwanted side reactions. The compound is especially valuable in synthesizing peptides with aspartic acid residues, as it maintains stability under standard SPPS conditions. After the peptide chain is assembled, the Fmoc and OtBu groups can be removed using appropriate deprotection methods, such as piperidine for Fmoc and trifluoroacetic acid (TFA) for OtBu, revealing the free aspartic acid residue in the final peptide product. Its use is critical in producing peptides for research, pharmaceuticals, and biotechnology applications.