Separation and identification of an impurity from the istradefylline intermediate.

Istradefylline is a selective adenosine antagonist for the A 2a receptor, and it is used to treat the Parkinson's disease and improve dyskinesia in the early stage of the Parkinson's disease. An impurity in the istradefylline intermediate A 1 (6-amino-1,3-diethyl-2,4-(1 H ,3 H )-pyrimidinedione) was identified by high performance liquid chromatography (HPLC); it was separated by preparative HPLC and further characterized by UV, IR, MS, NMR, 2D NMR and single-crystal XRD analyses. The impurity was identified as ( E )- N -ethyl-2-cyano-3-ethylamino-2-butenamide, which originated from the synthetic process of the intermediate A 1 . The structure of this impurity might affect the efficiency and safety of istradefylline; therefore, the research and control of this impurity are necessary for ensuring the quality of istradefylline.