(S)-3-Amino-2-methylpropanoic acid, also known as (S)-3-Amino-2-methylpropionic acid or (S)-β-Aminoisobutyric acid, is a non-proteinogenic amino acid. It is a chiral compound with a methyl group at the β-position relative to the carboxylic acid group. This structure makes it a valuable building block in organic synthesis and biochemical research. This compound is a key metabolite in the catabolism of thymine and valine. It has been studied in the context of metabolic disorders and as a potential biomarker. In pharmaceutical research, it serves as a crucial chiral intermediate for the synthesis of various bioactive molecules and drug candidates, particularly those requiring specific stereochemistry. Its role extends to the preparation of peptides and peptidomimetics. As a specialty amino acid derivative, it is primarily used in research settings for exploring metabolic pathways and developing novel therapeutic agents. It is commercially available as a high-purity reagent for laboratory use.