A solution of 2,2-dimethyl-1-[2-(3,4,5-trimethoxy-phenyl)-5-(2-trimethylsilanyl-ethoxymethyl)-5H-pyrrolo[2,3-b]pyrazin-7-yl]-pent-4-en-1-one (0.127 g, 0.242 mmol) in 4 mL of dichloromethane and 1 mL of trifluoroacetic acid was stirred for 3 h, then concentrated. The residue was taken up in 2 mL of ethanol (not all dissolves) and treated with sodium acetate trihydrate (0.329 g, 2.42 mmol). The mixture was stirred for 4 d, then concentrated to a residue. Column chromatography (0→5% MeOH/CH2Cl2) afforded 0.048 g (50%) of 2,2-dimethyl-1-[2-(3,4,5-trimethoxy-phenyl)-5H-pyrrolo[2,3-b]pyrazin-7-yl]-pent-4-en-1-one as a white solid.
