Isosorbide-5-mononitrate (0.203 g, 1.06 mmol) was added to a stirred solution of 1-methyl-1-{[(4-nitrophenoxy)carbonyl]oxy}ethyl 2-ethoxy-1-{[2′-(1-trityl-1H-tetrazol-5-yl)biphenyl-4-yl]methyl}-1H-benzimidazole-7-carboxylate (Intermediate 1, 0.800 g, 0.883 mmol), 4-dimethylaminopyridine (0.162 g, 1.33 mmol) and scandium trifluoromethanesulfonate (0.087 g; 0.177 mmol) in dichloromethane (12 mL). The solution was stirred at room temperature for 24 hours. Then the mixture was diluted with dichloromethane, washed with aqueous sodium dihydrogenphosphate (20 mL) and brine (20 mL); the organic layer was dried over sodium sulfate and concentrated under reduced pressure. The residue was purified by flash chromatography (Biotage SP1; column 40+M; TLC method: n-hexane/ethyl acetate: 6/4; Rf=0.33) to afford a solid that was dissolved in methanol (8 mL). The mixture was stirred at 40° C. for 5 hours, at 60° C. for 2 hours, and at room temperature for 18 hours. Then the solution was concentrated under reduced pressure. The residue was purified by flash chromatography (Biotage SP1; column 25+M; dichloromethane/methanol: 98/2), affording the title compound as a white solid. 1H NMR (300 MHz, CDCl3) δ 8.03 (d, 1H), 7.69-7.58 (m, 2H), 7.48 (d, 1H), 7.31 (d, 1H), 6.88 (t, 1H), 6.80 (d, 2H), 6.76-6.62 (m, 3H), 5.60 (s, 2H), 5.41-5.33 (m, 1H), 5.03 (d, 1H), 4.95 (t, 1H), 4.48 (d, 1H), 4.36-4.15 (m, 2H), 4.10-3.86 (m, 3H), 1.62 (d, 6H) 1.43 (t, 3H).
