(S)-3-Aminobutanoic acid ethyl ester hydrochloride is a chiral organic compound featuring an ethyl ester group and a primary amine functionality, both attached to a butanoic acid backbone. The amine group is protected as its hydrochloride salt, enhancing its stability and handling properties. Its molecular formula is C6H14ClNO2. This compound serves as a crucial chiral building block in pharmaceutical synthesis. Its primary application is as a key intermediate in the production of various active pharmaceutical ingredients (APIs). Notably, it is extensively used in the synthesis of chiral β-amino acid derivatives and peptidomimetics, which are important scaffolds in drug discovery for conditions such as neurological disorders and metabolic diseases. The (S)-configuration is essential for imparting specific biological activity in the final drug molecules. As a readily available chiral synthon, it is valuable in asymmetric synthesis and medicinal chemistry research. It is typically handled under inert atmosphere due to the sensitivity of the free amine and stored in a cool, dry place.