To a solution of tert-butyl (2S,4S)-2-[9-(2-{(2S)-1-[N-(methoxycarbonyl)-O-methyl-L-threonyl]pyrrolidin-2-yl}-1H-imidazol-5-yl)-1,11-dihydroisochromeno[4′,3′:6,7]naphtho[1,2-d]imidazol-2-yl]-4-(methoxymethyl)pyrrolidine-1-carboxylate (0.20 g, 0.26 mmol) in a mixture of CH2Cl2 (3.0 mL) and MeOH (0.5 mL) was added HCl (in dioxanes, 4M, 2.0 mL, 8.0 mmol). The solution was stirred at 40° C. for 1 h, and then cooled to room temperature and concentrated to dryness under reduced pressure. To the crude intermediate suspended in CH2Cl2 (3.0 mL) was added (R)-2-(methoxycarbonylamino)-2-phenylacetic acid (0.081 g, 0.39 mmol) and DIPEA (0.150 mL, 0.86 mmol). The resulting solution was cooled to −40° C. and COMU (0.180 g, 0.42 mmol) was added. The reaction was allowed to slowly warm to room temperature over 30 min and maintained for 1.5 h. The solution was diluted with CH2Cl2 and washed with aqueous bicarbonate. The aqueous layer was backextracted with CH2Cl2. The combined organic layers were dried over Na2SO4 and concentrated under reduced pressure. The crude residue was purified by preparative reverse phase HPLC (10% to 50% MeCN/water with 0.1% TFA). The desired fractions were combined and concentrated under reduced pressure to remove volatile organics. The addition of aqueous sodium bicarbonate with stirring resulted in precipitation of a white solid. The precipitate was filtered through a membrane filter and washed with water. Drying under reduced pressure afforded methyl {(1R)-2-[(2S,4S)-2-(9-{2-[(2S)-1-{(2S,3R)-3-methoxy-2-[(methoxycarbonyl)amino]butanoyl}pyrrolidin-2-yl]-1H-imidazol-5-yl}-1,11-dihydroisochromeno[4′,3′:6,7]naphtho[1,2-d]imidazol-2-yl)-4-(methoxymethyl)pyrrolidin-1-yl]-2-oxo-1-phenylethyl}carbamate (0.10 g, 46%). 1H-NMR: 400 MHz, (MeOD) δ: (Mixture of rotamers) 8.34 (s, 1H), 7.92-7.97 (m, 2H), 7.33-7.69 (m, 10H), 5.53 (s, 1H), 5.36-5.39 (m, 1H), 5.15-5.21 (m, 3H), 4.44 (d, 1H), 3.86-3.93 (m, 2H), 3.68-3.75 (m, 2H), 3.66 (s, 3H), 3.65 (s, 3H), 3.46-3.57 (m, 2H), 3.28 (s, 3H), 3.19 (s, 3H), 2.47-2.60 (m, 3H), 2.22-2.36 (m, 4H), 1.99-2.08 (m, 3H), 1.15 (d, 3H). MS (ESI) m/z 886.19 [M+H]+.
