1.45 g of (6-methoxyquinolin-7-yl)acetaldehyde and 0.63 g of 1,4-dioxa-8-azaspiro[4.5]decane were dissolved in 20 ml of methylene chloride. Thereafter, 0.42 ml of acetic acid and 0.74 g of sodium triacetoxyborohydride were added to the reaction solution, and the obtained mixture was then stirred at room temperature for 3 hours. Thereafter, a saturated sodium bicarbonate aqueous solution was added to the reaction solution, followed by extraction with methylene chloride. The extract was dried over magnesium sulfate and then concentrated under a reduced pressure. The residue was purified by silica gel column chromatography (chloroform-methanol), so as to obtain 445 mg of the subject compound.
