Tert-butyl (2S,4S)-2-[9-(2-{(2S,4S)-1-[N-(methoxycarbonyl)-L-valyl]-4-methylpyrrolidin-2-yl}-1H-imidazol-5-yl)-1,11-dihydroisochromeno[4′,3′:6,7]naphtho[1,2-d]imidazol-2-yl]-4-methylpyrrolidine-1-carboxylate (257 mg, 0.34 mmol) was dissolved in DCM (4 mL), MeOH (1 mL) and HCl (4 M in dioxane, 1 mL) was added. The reaction mixture was stirred for 3 h and then concentrated under reduced pressure. The crude residue was treated with (R)-2-(methoxycarbonylamino)-2-phenylacetic acid (71 mg, 0.34 mmol), COMU (161 mg, 0.34 mmol) and DMF (6 mL), then DIPEA (0.3 mL, 1.67 mmol) was added dropwise. After 15 h, the mixture was diluted with 10% MeOH/EtOAc and washed successively with saturated aqueous NaHCO3 and brine. The organics were dried over MgSO4, filtered and concentrated under reduced pressure. The crude residue was purified by HPLC to afford methyl {(2S)-1-[(2S,4S)-2-(5-{2-[(2S,4S)-1-{(2R)-2-[(methoxycarbonyl)amino]-2-phenylacetyl}-4-methylpyrrolidin-2-yl]-1,11-dihydroisochromeno[4′,3′:6,7]naphtho[1,2-d]imidazol-9-yl}-1H-imidazol-2-yl)-4-methylpyrrolidin-1-yl]-3-methyl-1-oxobutan-2-yl}carbamate (152 mg, 53%). LCMS-ESI+: calculated for C48H52N8O7: 852.40; observed [M+1]+: 854.26. 1H NMR (CD3OD): 8.677 (s, 1H), 8.232-7.837 (m, 5H), 7.695-7.673 (m, 2H), 7.496-7.426 (m, 5H), 5.499 (s, 1H), 5.445-5.401 (m, 1H), 5.337 (s, 1H), 5.253-5.208 (q, 1H, J=7.2 Hz), 4.870 (m, 1H), 4.230 (d, 1H, J=7.2 Hz), 3.781 (m, 1H), 3.671 (s, 3H), 3.607 (s, 3H), 3.425 (m, 3H), 2.750-2.689 (m, 2H), 2.683 (m, 2H), 2.384 (m, 1H), 1.894 (quint, 2H, J=12 Hz), 1.249-1.151 (m, 6H), 0.974-0.890 (m, 6H).
