Synthesis of labeled ambroxol and its major metabolites

Abstract Ambroxol is a mucolytic agent used in the treatment of respiratory diseases. Herein, we report the synthesis of carbon‐14‐labeled ambroxol with the radioactive atom(s) either on the benzylic carbon or uniformly in the cyclohexyl ring with specific activities of 59 and 81 mCi/mmol, respectively. We also describe the preparation of deuterium‐labeled ambroxol, its deuterium‐labeled tetrahydroquinazoline metabolite (DHTQ), carbon‐13‐labeled 3,5‐dibromoanthranilic acid metabolite, as well as an unlabeled O ‐glucuronide conjugate. Copyright © 2009 John Wiley & Sons, Ltd.