A Mixture of 3-(4-fluoro-benzenesulfonyl)-1-trityloxy-azepan-2-one prepared from step F (18.9 mg, 0.0357 mmol), 4-methoxy-phenol (19.2 mg, 0.154 mmol) and K2CO3 (38.1 mg, 0.275 mmol) in anhydrous DMA (1.5 mL) was stirred and heated at 100° C. for overnight. The reaction mixture was diluted with EtOAc and washed sequentially with water and saturated NaCl solution. The organic phase was then dried over anhydrous Na2SO4 and concentrated under reduced pressure to gave a crude material, which was then purified by a column chromatography (0˜25% EtOAc in hexane). MS: 656.5 (M+Na)+.
