Synthesis of [3H] vardenafil,Levitra®, using a new labeling technique

Tritium was introduced into the new orally active, selective phosphodiesterase type V (PDE V) inhibitor vardenafil (Levitra^®), by reduction of a suitable amide precursor with freshly prepared lithium aluminum tritide. A specific activity of 52.7 Ci/mmol (1.95 TBq/mmol) was achieved. In order to overcome the usual technical difficulties during the preparation of complex tritides a new and easy labeling technique which has considerable potential for various tritia‐tion procedures, was developed. Copyright © 2003 John Wiley & Sons, Ltd.