Used as a chiral building block in the synthesis of peptide-based pharmaceuticals. Its protected amine group (with Boc) and free carboxylic acid allow selective coupling reactions, making it valuable in solid-phase peptide synthesis. The (S)-configuration ensures stereochemical control, which is critical for biological activity in drug development. The unsaturated side chain provides opportunities for further functionalization. Commonly employed in the preparation of enzyme inhibitors and bioactive molecules where precise stereochemistry is required.