The method of preparing a quaternary ammonium salt of morphine brominated furans

The present invention relates to a process for preparing brominated morphinan quaternary ammonium salt, the method comprising an ion exchange resin to exchange the bromomethyl naltrexone methylnaltrexone bromide with an iodide mixture through a type strongly basic anion-bromo, simplify purification operations, improve product purity suitable for industrial production.