S-(5-Mercapto-2-nitrobenzoic Acid)-D-penicillamine Disulfide-d6 is deuterium labeled S-(5-Mercapto-2-nitrobenzoic Acid)-D-penicillamine Disulfide (M254020), which is Penicillamine (P223000) derivatized with 2-nitro-5-thiobenzoic acid. D-Penicillamine is a penicillin metabolite used in the treatment of Wilson’s disease, Cystinuria, Scleroderma and arsenic poisoning.