Determination of the binding situation of pyridine in xylan sulfates by means of detailed NMR studies

Abstract Xylan sulfate is an important drug to treat interstitial cystitis. Production of the drug by sulfation of the polysaccharide with a sulfating agent like chlorosulfuric acid and pyridine–SO 3 complex in pyridine may lead to products containing pyridine‐based impurities. Xylan sulfate containing nitrogen is investigated by different NMR measurements in order to clarify the binding situation of pyridine. The detailed NMR studies allow the conclusion that the pyridine‐based impurities are covalently bonded to the reducing end group. Furthermore, the NMR spectroscopic investigation indicates that the side reactions occur at shorter polymer chains only.