Synthesis
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.
References
[1] Patent: US2011/92475, 2011, A1. Location in patent: Page/Page column 18
[2] Patent: WO2006/64196, 2006, A1. Location in patent: Page/Page column 138-139
[3] Patent: US2005/261291, 2005, A1. Location in patent: Page/Page column 67
[4] Patent: US6194409, 2001, B1
[5] Patent: EP1621537, 2006, A1. Location in patent: Page/Page column 52
