3-O-Methyltolcapone-D7 is a deuterium labeled 3-O-Methyltolcapone. 3-O-Methyltolcapone (T10119) (Ro 40-7591) is a metabolite of Tolcapone which is a potent COMT inhibitor. Tolcapone crosses the blood-brain barrier and can be used for treatment of Parkinson's disease.