In a similar manner to Step 2 of Example 6, 4-chloro-7-[1-(tert-butoxycarbonyl)-5-formylindol-2-yl]isoindolinone (30.0 mg, 0.0730 mmol) was dissolved in acetonitrile (2 mL), and the solution was treated with 4-piperidineethanol (94 mg, 0.73 mmol), acetic acid (0.168 mL, 2.93 mmol) and sodium triacetoxyborohydride (54 mg, 0.26 mmol). The reaction mixture was added with 1 mol/L hydrochloric acid and ethyl acetate, followed by extracting with 1 mol/L hydrochloric acid. The aqueous layer was added with sodium carbonate to adjust the pH to 9. The mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to obtain 4-chloro-7-{1-(tert-butoxycarbonyl)-5-[4-(2-hydroxyethyl)piperidinomethyl]indol-2-yl}isoindolinone (42.2 mg).
