(2S,4S)-tert-butyl 4-methyl-2-(9-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,11-dihydorisochromeno [4′, 3′:6,7] naptho[1,2-d]imidazol-2-yl)pyrrolidine-1-carboxylate (558 mg, 0.96 mmol), methyl(S)-1-((2S,4S)-2-(5-iodo-1H-imidazol-2-yl)-4-methylpyrrolidin-1-yl)-3-methyl-1-oxobutan-2-ylcarbamate (501 mg, 1.15 mmol), Pd(PPh3)4 (111 mg, 0.096 mmol), PdCl2(dppf)2 (70 mg, 0.096 mmol), and K2CO3 (2M in H2O, 1.6 mL, 3.17 mmoL) were combined in DMSO (6 mL) and dioxane (6 mL). The mixture was degassed with bubbling N2 for 10 min then heated to 95° C. for 14 h. After cooling, the reaction mixture was diluted with 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 silica column chromatography (0%-30% MeOH/EtOAc) to afford 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, 35%).
