To a solution of Compound 8 (9.8 g, crude, containing lithium chloride) in N,N-dimethylformamide (100 mL) was added hydroxybenzotriazole (6.22 g, 46.07 mmol), 2-oxa-7-azaspiro[3.5]nonan hemioxalate (4.39 g, 34.56 mmol), N,N-diisopropylethylamine (8.93 g, 69.11 mmol) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (8.83 g, 46.07 mmol) sequentially. The reaction mixture was stirred overnight at room temperature and then poured into water (800 mL). Gray solid formed was collected by filtration. This solid was purified by flash chromatography (gradient from dichloromethane to dichloromethane:methanol 10:1) to give Compound 9 (5.20 g) as an off-white solid. m/z 535.3 (M+H, 100%) (positive ionization mode). 1H-NMR (CDCl3, 400 MHz): δ 1.83 (4H, m); 2.27 (2H, m); 2.30 (3H, s); 2.46 (2H, t); 3.41 (2H, t); 3.42 (2H, t); 4.05 (3H, s); 4.27 (2H, t); 4.46 (4H, q); 6.34 (1H, q); 7.0 (1H, dd); 7.10 (1H, d); 7.34 (1H, s); 7.63 (1H, s); 8.17 (1H, s); 8.60 (1H, s).
