Fmoc-(S)-3-Amino-4-(3-benzothienyl)-butyric acid is primarily used in peptide synthesis as a building block. Its Fmoc protecting group allows for selective deprotection during solid-phase peptide synthesis, making it valuable for constructing complex peptides. The benzothienyl moiety provides unique structural and electronic properties, which can be leveraged in designing peptides with specific biological activities or binding affinities. This compound is particularly useful in medicinal chemistry for developing peptide-based drugs, where its incorporation can enhance interactions with target proteins or improve pharmacokinetic properties. Additionally, it finds application in research focused on peptide mimetics and bioactive peptide design.