Identification, synthesis, and characterization of β-isomer as process related impurity in production of methocarbamol from guaifenesin

Abstract

Methocarbamol is a central nervous system depressant with skeletal muscle relaxant properties indicated to treat spasms. During the synthesis of methocarbamol from guaifenesin, both potential known and an unknown impurity (0.05%-0.1%), high performance liquid chromatography) were observed. The later was separated using preparative liquid chromatography. Upon the findings of the 1H nuclear magnetic resonance, Mass, and IR spectral analysis, the unknown impurity was designated as a β-isomer of methocarbamol [1-hydroxy-3-(2-methoxy phenoxy) propan-2-yl carbamate]. The impurity isolation, its structure elucidation, and the potential formation mechanism are discussed.