S-(-)-4-Bromo-alpha-phenylethylamine is primarily used in organic synthesis as a chiral building block for the production of various pharmaceuticals and fine chemicals. Its stereochemistry makes it valuable in the development of enantiomerically pure compounds, particularly in the synthesis of drugs where chirality plays a critical role in biological activity. It is also employed in asymmetric synthesis to create complex molecules with high optical purity, which is essential in the production of active pharmaceutical ingredients (APIs). Additionally, it serves as a precursor in the preparation of ligands for catalytic systems used in chemical reactions, enhancing selectivity and efficiency.