Identification and Synthesis of Impurities in Pinocembrin–A New Drug for the Treatment of Ischemic Stroke

Four minor impurities in pinocembrin ( 1 )–a new drug to treat ischemic stroke, were analysed and identified by means of HPLC‐UV‐MS analysis, spectroscopic evidences and chemical synthetic methods. Their chemical structures were identified as 5,7‐dihydroxy‐2‐phenyl‐4 H ‐1‐benzopyran‐4‐one ( 2 ), 3‐phenyl‐1‐(2,4,6‐trihydroxyphenyl)‐1‐propanone ( 3 ), 5,7‐dihydroxy‐2‐cyclohexyl‐4 H ‐1‐benzopyran‐4‐one ( 4 ), and 2,3‐dihydro‐5,7‐dihydroxy‐2‐cyclohexyl‐4 H ‐1‐benzopyran‐4‐one ( 5 ), respectively. All of the impurities were side products of excessive hydrogenation of the target product 1 or the starting material 2 in the course of synthesis, and 5 was a new compound.