In a similar manner to Step 3 of Example 16, 4,5-dichloro-3-hydroxy-2-(1-methyl-1-phenylethyl)isoindolinone (400 mg, 1.19 mmol) was dissolved in THF (16 mL), and the solution was treated with TMEDA (0.718 mL, 4.76 mmol), sec-butyl lithium-hexane solution (0.99 mol/L, 4.8 mL, 4.76 mmol) and iodine (453 mg, 1.79 mmol), followed by purification by flash column chromatography (chloroform/methanol=95/5 to 90/10) to obtain 3-hydroxy-4,5-dichloro-7-iodo-2-(1-methyl-1-phenylethyl)isoindolinone (350 mg, yield 64%).
