(S)-2-(4-methoxyphenyl)-7-methoxy-8-(3-((S)-7-methoxy-2-(trifluoromethylsulphonyl)-5,11-dioxo-10-((2-(trimethylsilyl)ethoxy)methyl)-5,10,11,11a-tetrahydro-1H-pyrrolo[2,1-c][1,4]benzodiazepin-8-yloxy)propyloxy)-10-((2-(trimethylsilyl)ethoxy)methyl)-1H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10H,11aH)-dione (1-Compound 17 in WO 2010/043880)(0.093 g, 0.086 mmol), benzyl 4-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)piperazine-1-carboxylate (2)(0.047 g, 0.110 mmol, 1.3 eq) and sodium carbonate (0.009 g, 0.140 mmol, 1.5 eq) were suspended in ethanol (1.5 mL), toluene (3 mL) and water (1.5 mL) under an argon atmosphere. Pd(PPh3)4 (0.002 g, 0.002 mmol, 0.02 eq) was added to the mixture, and the reaction was stirred overnight at room temperature. EtOAc (10 mL) was added to the mixture and the organic phase was washed with brine (15 mL) and dried over MgSO4, and the solvent was removed by rotary evaporation under reduced pressure. The crude was purified by flash column chromatography (silica gel, gradient 20% EtOAc/80% hexane-100% EtOAc). Compound 3 was obtained as a yellow solid (0.0549 g, 52%); Rf 0.21 [50% EtOAc-50% hexane]; LC-MS (5 min) 3.92 min, ES+ 1221.39.
