N-Acetyl-S-(3-hydroxypropyl)cysteine

N-Acetyl-S-(3-hydroxypropyl)cysteine is a cysteine derivative featuring an N-acetyl group, a thiolate sulfur linked to a 3-hydroxypropyl chain, and a terminal hydroxyl group. Its structure incorporates both hydrophilic (hydroxyl) and lipophilic (acetyl) moieties, conferring moderate polarity. This compound arises as a synthetic byproduct during acetylation processes of thiol-containing APIs, where side-chain hydroxylation occurs. The 3-hydroxypropyl substitution introduces steric hindrance, influencing reactivity and stability. Utilized as an HPLC reference standard for quantifying process-related impurities in cysteine-based pharmaceuticals.