Used in solid-phase peptide synthesis as a chiral building block for incorporating non-natural amino acid residues into peptides. The Fmoc group provides orthogonal protection for the amine, allowing stepwise assembly of peptide chains under mild basic conditions. The butenyl side chain offers a site for further functionalization, such as cross-metathesis or hydrofunctionalization, enabling the introduction of labels, cyclic structures, or modified side chains in peptide-based drug design and chemical biology research. Its stereochemistry ensures precise control over three-dimensional structure, which is critical for biological activity in synthetic peptides.