Step 4:Preparation of intermediate 7
Intermediate 6 (0.48g, 1.75mmol, 1.0 eq) and MeCN (9mL, c=0.2)
was added in sealed tube. To this solution, EtI (2mL, 14.0 eq) was
added. After addition, the reaction mixture was stirred at 90℃ for 10h.
After completion, the reaction
mixture was concentrated under reduce pressure. The residue was purified
by column chromatography to give intermediate 7 (470mg,
yield=62.6%, HPLC: 99%) as a solid.