1.31 g of the product of Example 172 was dissolved in 3 ml of dimethylformamide, to the solution were added 644 mg of 1,2-dibromoethane and 1.13 g of anhydrous potassium carbonate at a room temperature, and the mixture was stirred for 24 hours. After adding 100 ml of ethyl acetate, the ethyl acetate layer was sequentially washed with water and a saturated sodium chloride aqueous solution twice in each case, and dried over magnesium sulfate. The solution was filtered and evaporated under a reduced pressure, and resulting residue was purified on a silica gel column (silica gel 50 g, eluant: 5% methanol in chloroform), to obtain 356 mg of the title compound in a colorless amorphous form, while recovering the residual starting material.
