(S)-2-Aminobutanoic acid tert-butyl ester hydrochloride is a chiral amino acid derivative. It is a white to off-white crystalline powder, typically used as a protected form of (S)-2-aminobutyric acid. The tert-butyl ester group serves as a common protecting group for carboxylic acids in peptide synthesis and organic chemistry. This compound is primarily employed as a key chiral building block in the pharmaceutical industry for the synthesis of active pharmaceutical ingredients (APIs) and complex bioactive molecules. Its chiral center makes it valuable for constructing peptides and peptidomimetics with specific stereochemistry. It finds application in research and development of drugs targeting various therapeutic areas. As a protected amino acid ester, it is a versatile intermediate in solid-phase peptide synthesis (SPPS) and solution-phase organic synthesis. Handling requires standard precautions for amino acid derivatives and hydrochloride salts.