Used as a chiral building block in the synthesis of pharmaceuticals, particularly in the preparation of protease inhibitors and other biologically active molecules. Its aldehyde functionality allows for facile formation of carbon-carbon bonds via nucleophilic addition or condensation reactions, while the trityl group provides steric bulk and aids in solubility during purification steps. The (S)-configuration ensures stereochemical control in asymmetric syntheses, making it valuable in the development of enantiomerically pure drugs. Commonly employed in multi-step organic syntheses where preservation of chirality is critical.