In a similar manner to Step 2 of Example 6, 4-methyl-7-[1-(tert-butoxycarbonyl)-5-formylindol-2-yl]isoindolinone (100 mg, 0.256 mmol) was dissolved in acetonitrile (8 mL), and the solution was treated with 1-(2-hydroxyethyl)piperazine (133 mg, 1.02 mmol), acetic acid (0.307 mL, 5.12 mmol) and sodium triacetoxyborohydride (218 mg, 1.02 mmol). The reaction mixture was added with 1 mol/L hydrochloric acid and extracted with ethyl acetate. The organic layer was washed with sodium carbonate and saturated brine, and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to obtain 4-methyl-7-(1-(tert-butoxycarbonyl)-5-[4-(2-hydroxyethyl)pyperazin-1-ylmethyl]indol-2-yl)isoindolinone (126 mg, yield 98%).
