(S)-But-3-yn-2-amine hydrochloride is primarily used in organic synthesis as a chiral building block. It serves as a key intermediate in the production of pharmaceuticals, particularly in the development of drugs that require specific stereochemistry for efficacy. The compound is often employed in asymmetric synthesis to create enantiomerically pure substances, which are crucial in the manufacture of active pharmaceutical ingredients (APIs). Additionally, it finds application in the synthesis of biologically active compounds, including those with potential therapeutic effects in neurological and psychiatric disorders. Its utility in medicinal chemistry is further highlighted by its role in the preparation of compounds that target specific enzymes or receptors, aiding in the discovery of new drugs.