Isolation and structural identification of an impurity in fluconazole bulk drug substance

Four impurities in fluconazole API sample obtained from a recently proposed synthetic process were detected by HPLC. One of the impurities was unknown having not been reported previously. This less polar unknown impurity was isolated from the crude sample of fluconazole bulk drug using semi-preparative HPLC. Structure of impurity was elucidated as 2-(2-(dimethylamino)-4-fluorophenyl)-1,3-di(3H-1,2,4-triazol-1-yl)propan-2-ol by using NMR spectroscopy(1H, 13C, 19F, 1H–1H, 1H–13C, HMBC and nOe) and mass spectrometry. The formation and synthesis of the impurity was discussed.