4045-25-4

188622-27-7

4045-25-4

Step 3: Preparation of Intermediate 41a; To a 1,4-dioxane (5 mL) solution of Intermediate 40a (810 mg, 3.76 mmol) under stirring was slowly added a 1,4-dioxane solution (8 mL) of 4M HCl at 0 °C. The reaction mixture was kept at 0°C and stirring was continued for 2 hours. Subsequently, the reaction system was warmed up to 23 °C and the organic solvent was evaporated under reduced pressure. The resulting residue was washed with anhydrous ether and finally dried under vacuum to give Intermediate 41a (430 mg, yield > 99%) in the form of hydrochloride.