After 3 days，the reaction mixture was diluted with toluene (100 mL) and the volatiles were removed by rotary evaporation.  The residue was diluted with ether (400 mL) and washed with NaOH (10% w/v, 4 × 140 mL) and brine (1 × 120 mL).  The organic layer was dried over MgSO4 (anhyd), filtered, and the volatiles were removed by rotary evaporation to yield a clear yellow oil。Then Dess-Martin periodinane was added to a solution of this product in DCM  and the resulting reaction mixture was stirred at 0℃  overnght。