Synthesis of telmisartan impurity B.

Telmisartan is an antihypertensive drug and is a specific angiotensin II receptor (AT1) antagonist. According to European Pharmacopoeia 7 Edition 2008 telmisartan quality standard, there are seven impurities in telmisartan. Impurity B which is not available commercially and no synthetic method is published so far. We report herein the first synthesis of impurity B. The structure of impurity B was confirmed by 1H NMR, 13C NMR and MS data. These findings should be important for quality control purposes in the manufacture and quality control of telmisartan.