2-(Benzyl(1-(4-methoxyphenyl)propan-2-yl-d6)amino)-1-(4-(benzyloxy)-3-nitrophenyl)ethanone is the labeled analogue of 2-(Benzyl(1-(4-methoxyphenyl)propan-2-yl)amino)-1-(4-(benzyloxy)-3-nitrophenyl)ethanone (B2855650), which is used in the preparation of 3-acylamino-4-hydroxy-α-(N-substituted aminomethyl)benzyl alcohol derivatives as β-adrenoreceptor stimulants.