N-(4-Fluorophenyl)-2-methyl-N-[1-(2-phenylethyl)-4-piperidinyl]-propanamide-d7 is deuterium labeled N-(4-Fluorophenyl)-2-methyl-N-[1-(2-phenylethyl)-4-piperidinyl]-propanamide (F489575).N-(4-Fluorophenyl)-2-methyl-N-[1-(2-phenylethyl)-4-piperidinyl]-propanamide is an impurity of Furanylfentanyl (F864085), which is an opiod analgesic agent and an analog of Fentanyl (F275000).In addition, N-(4-Fluorophenyl)-2-methyl-N-[1-(2-phenylethyl)-4-piperidinyl]-propanamide may be a useful compound for developingfentanyl-conjugated vaccines by utilizinga protein–drug conjugate that generates anin vivo immunoantagonist, which can minimize the concentration of a specific drug at the sites of action.