Piperonal-D3 is an intermediate used in the synthesis of DL-threo-Droxidopa-d3 (D689953), which is an isotope labelled compound of DL-threo-Droxidopa (D689950), a synthetic amino acid precursor of Norepinephrine. An antiparkinson; Also, it is the deuterated form of Piperonal (P490050), which is an impurity of Tadalafil (T004500). Tadalafil impurity A.