(S)-4-Amino-3-(4-chlorophenyl)butanoic acid is a chiral, non-proteinogenic amino acid derivative. It features a 4-chlorophenyl group and a butanoic acid backbone with an amino group at the gamma position. This specific (S)-enantiomer is a key synthetic intermediate in the production of important pharmaceutical compounds. Its primary and most significant application is in the synthesis of Baclofen, a gamma-aminobutyric acid (GABA) derivative used as a muscle relaxant and antispastic agent for treating conditions like multiple sclerosis and spinal cord injuries. The (S)-enantiomer is the pharmacologically active form of Baclofen. This compound serves as a crucial chiral building block, enabling the efficient and stereoselective construction of the GABAergic pharmacophore essential for the drug's biological activity. As a high-value pharmaceutical intermediate, its synthesis and supply are critical for the manufacturing of the active pharmaceutical ingredient (API) Baclofen. Its chirality is paramount, as the biological activity resides predominantly in this specific stereoisomer.