(R)-3-Amino-3-(3-methoxyphenyl)propanoic acid is a chiral non-proteinogenic amino acid derivative. It features a β-amino acid scaffold with a 3-methoxyphenyl substituent at the β-position. This compound is a key chiral building block in pharmaceutical synthesis. Its primary and most significant application is as a crucial intermediate in the synthesis of (R)-Baclofen, a selective GABA_B receptor agonist used as a muscle relaxant and antispastic agent for treating conditions like multiple sclerosis and spinal cord injuries. The (R)-enantiomer is the pharmacologically active form. The synthesis of this specific stereoisomer is critical for drug efficacy, making this chiral intermediate highly valuable in the production of the active pharmaceutical ingredient (API). This compound exemplifies the importance of chiral intermediates in modern asymmetric synthesis for central nervous system (CNS) drugs. Its use is specialized within the context of Baclofen production rather than as a general-purpose synthetic reagent.