(S)-5-(1,2-Dithiolan-3-yl)pentanoic acid, known as (S)-α-lipoic acid, is the unnatural enantiomer of the antioxidant α-lipoic acid. It serves as a key intermediate in pharmaceutical synthesis and stereoselective reactions. Primarily utilized in research to investigate enantiomeric effects on biological systems, including mitochondrial function and oxidative stress mechanisms, it exhibits lower antioxidant activity compared to the natural (R)-enantiomer. This specialty chemical is also applied in the development of nutraceuticals, dietary supplements for metabolic studies, and skincare formulations exploring stereospecific protection against free radicals and UV damage.