The product from Step 6 (40 mg, 0.067 mmol) was combined with dimethylamine (0.13 mmol, 2 M in THF) and AcOH (7.5 μL, 0.13 mmol) in 1,2-dichloroethane (1 mL). The mixture was stirred at room temperature for 30 min. Sodium triacetoxyborohydride (28 mg, 0.13 mmol) was added to the solution. The mixture stirred 30 min at room temperature, and then was partitioned between CH2Cl2 (4 mL) and aqueous 1 M K2CO3 (4 mL). The organic layer was loaded onto silica gel and eluted with 0-10% MeOH in CH2Cl2 to afford the title compound (36 mg, 86%). LC-MS 626.6 [M+H]+, RT 1.26 min.
