0.2 g of the product of Example 172 and 0.13 g of p-hydroxybenzaldehyde were dissolved in 10 ml of methanol, to the solution were added 60 mg of sodium cyanoborohydride and two drops of acetic acid, and the mixture was stirred for 2 days at a room temperature. The reaction mixture was concentrated under a reduced pressure, and after adding a saturated sodium chloride aqueous solution, extracted three times with 20 ml of ethyl acetate. The extracts were combined, washed with sodium chloride, dried over magnesium sulfate, filtered and concentrated under a reduced pressure. The resulting residue was purified on a silica gel column (silica gel 10 g, eluant: 2% methanol in chloroform), to obtain 150 mg of the title compound in a colorless amorphous form.
