Compound 4b (46.33 g, 100 mmol) and toluene (463 mL) were added to a three-neck flask.After stirring uniformly, trifluoroacetic acid (18.02 g, 300 mmol) was slowly added.Heat to 75-80 ?? C for 6-8 hours.The raw materials disappeared and then cooled to room temperature.Wash with 5% sodium hydroxide solution (463 mL).Washed once with saturated saline (231 mL),Dry over sodium sulfate, filter,The filtrate was added with ammonium acetate (38.54 g, 500 mmol).Heating and refluxing for 10 to 16 hours,The reaction was cooled to room temperature.Add water (463 mL),Dispensing after stirring,The aqueous phase was extracted once more with toluene,The combined organic phases were washed with saturated brine (231 mL).Dry with sodium sulfate,Concentrated to remove the solvent,Isopropanol petroleum ether mixed solvent recrystallized,Filter, dryCompound 6b (31.64 g, 2 steps 76%) was dried.
