To a solution of (2S,4S)-tert-butyl 4-(methoxymethyl)-2-(9-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,11-dihydroisochromeno[4′,3′:6,7]naphtho[1,2-d]imidazol-2-yl)pyrrolidine-1-carboxylate (438 mg, 0.72 mmol), methyl(S)-1-((2S,4S)-2-(5-bromo-1H-imidazol-2-yl)-4-methylpyrrolidin-1-yl)-3-methyl-1-oxobutan-2-ylcarbamate (276 mg, 0.72 mmol), tetrakis(triphenylphosphine) palladium(0) (41 mg, 0.04 mmol) and dichloro[1,1′-bis(diphenylphosphino) ferrocene]palladium(II) (52 mg, 0.07 mmol) in a mixture of 1,2-dimethoxyethane (8.6 mL) and dimethylformamide (1.5 mL) was added a solution of potassium carbonate (2M in water, 1.07 mL, 2.15 mmol). The resulting mixture was degassed and then heated to 85° C. under argon for 18 hours. After cooling to room temperature, the reaction was diluted with ethyl acetate. The organics were washed with water and brine, dried (Na2SO4), and concentrated. The crude residue was purified by flash chromatography to yield tert-butyl (2S,4S)-2-[9-(2-{(2S,4S)-1-[N-(methoxycarbonyl)-L-valyl]-4-methylpyrrolidin-2-yl}-1H-imidazol-5-yl)-3,11-dihydroisochromeno[4′,3′:6,7]naphtho[1,2-d]imidazol-2-yl]-4-(methoxymethyl)pyrrolidine-1-carboxylate (182 mg, 32%).
