Preparation method for Delta-7 methylnaltrexone bromide

The invention discloses a preparation method for Delta-7 methylnaltrexone bromide and a preparation method for acetylated methylnaltrexone bromide, acetylated Delta-7 methylnaltrexone bromide, acetylated Delta-7 methylnaltrexone formate and Delta-7 methylnaltrexone formate. The Delta-7 methylnaltrexone bromide provided by the invention has potential genotoxicity and is applied to the impurity analysis in the preparation of raw pharmaceutical materials of methylnaltrexone bromide.