Fmoc-4-tert-butoxy-L-proline is widely used in peptide synthesis, particularly in solid-phase peptide synthesis (SPPS). It serves as a protected form of proline, where the Fmoc (fluorenylmethyloxycarbonyl) group protects the amino group, and the tert-butoxy group protects the hydroxyl group. This protection ensures selective reactions during peptide chain assembly, preventing unwanted side reactions. It is especially valuable in synthesizing complex peptides and peptidomimetics, where precise control over amino acid incorporation is critical. Additionally, its stability under standard SPPS conditions makes it a reliable building block for producing peptides used in drug development, biochemical research, and therapeutic applications.