(R)-Benzyl 3-((5-Acetamido-2-(benzyloxy)phenyl)thio-2-(benzylamino)propanoate is an intermediate used in the synthesis of rac-Acetaminophen Mercapturate-d5 (A172101), which is a labeled analogue and free acid of 3-(N-Acetyl-L-cystein-S-yl) Acetaminophen Disodium Salt (A172100), which is a metabolite of Acetaminophen (A161220). Acetaminophen is an analgesic and antipyretic agent used as a pain reliever to treat headache, muscle aches, and arthritis (1,2,3).