(S)-(-)-3-Benzoylthio-2-methylpropionic acid is a chiral organic compound featuring a carboxylic acid group and a benzoyl-protected thiol group on a methyl-substituted propionic acid backbone. Its specific (S)-configuration is crucial for its biological activity and synthetic utility. This compound is a key chiral intermediate in the synthesis of Captopril, a widely used angiotensin-converting enzyme (ACE) inhibitor for the treatment of hypertension and heart failure. The molecule serves as the precursor that provides the critical thiol-containing side chain with the correct stereochemistry, which is essential for binding to the active site of the ACE enzyme. As a protected thiol derivative, it offers stability during synthesis while allowing for deprotection to generate the active pharmacophore. Its primary industrial and research significance lies in the pharmaceutical manufacturing process of Captopril and related analogs.