Bubbling dry HCl through a methanol solution of 1-oxyl-3-carboxy-2,2,5,5-tetramethylpyrrolidine (I) for a short period of time leads to the nitroxide radical methyl ester (II). Reduction of (II) to the hydroxylamine (III) is then accomplished by treatment with hydrazine in MeOH. Alternatively, upon treatment of (I) with HCl/MeOH for longer than 24 h, this undergoes both esterification and reduction to the hydroxylamine methyl ester (III). Further acetylation of hydroxylamine (III) by using Ac2O in the presence of Et3N yields the title compound.