3.1.2. General Procedure for the Synthesis of Sulfonates **10a–d**

2.5 mmol of triethylamine was added to the suspension of 1 mmol of berberrubine hydrobromide in 25 mL of methylene chloride. 1.5 mmol of sulfochloride in 3 mL of methylene chloride was added under stirring at room temperature. After 5 hours the precipitate was filtered, washed with methylene chloride and the pure product **10a–d** was isolated.

3.1.3. 10-Methoxy-9-methanesulfonyloxy-2,3-methylenedioxyprotoberberine chloride (**10a**)
