Trifluoroacetic acid → 2-(3-((2-(cyclohex-1-en-1-yl)-4-((methylamino)methyl)-1H-pyrrol-1-yl)sulfonyl)phenoxy)-N,N-dimethylacetamide

tert-Butyl ((5-(cyclohex-1-en-1-yl)-1-((3-(2-(dimethylamino)-2-oxoethoxy)phenyl)sulfonyl)-1H-pyrrol-3-yl)methyl)(methyl)carbamate 8c (69 mg, 0.13 mmol) was dissolved in 8 mL of dichloromethane, and the reaction solution was cooled in an ice bath, followed by dropwise addition of 2 mL of trifluoroacetic acid. After removing the ice bath, the reaction solution was stirred at room temperature for 2 h. A saturated sodium bicarbonate solution was added dropwise until the pH of the reaction solution was 7 to 8, and then it was extracted with dichloromethane (20 mL×3). The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure. The resulting residue was purified by thin layer chromatography with elution system A to obtain the title product 2-(3-((2-(cyclohex-1-en-1-yl)-4-((methylamino)methyl)-1H-pyrrol-1-yl)sulfonyl)phenoxy)-N,N-dimethylacetamide 8 (39 mg, a colorless oil) in 69% yield.