Exposure of pyrrolidine (I) to NO in acetonitrile/ether in the presence of NaOMe in MeOH provides sodium 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (II), which is converted into the desired product by reaction with bromomethyl acetate (III) in DMSO in the presence of Na2CO3 and silver acetate (HgOAc).