Preparation of Highly Purified Nafronyl Oxalate and Its X-Ray Single Crystal Structure

Several different technological processes, including that of high vacuum fractionation, column chromatography and recrystallization, have been tried to reduce the quantity of impurities contained in the raw nafronyl oxalate. HPLC analysis showed that a combination of high vacuum distillation and water recrystallization led to a high quality product (99.6% purity), meeting the British Pharmocoepia (1998) standard. X-ray single crystal analysis confirmed the structure of the title compound as first reported.