To a solution of 4-amino-6,7-dimethoxy-3,4-dihydro-2H-quinoline-1,2-dicarboxylic acid 2-butyl ester 1-ethyl ester (Example 3) (500 mg, 1.30 mmol) in anhydrous dichloroethane (30 mL) was added acetic acid (79 mg, 1.30 mmol), followed by 3,5-bis(trifluoromethyl)benzaldehyde (318 mg, 1.30 mmol) and sodium triacetoxyborohydride (418 mg, 1.97 mmol). The reaction was stirred at room temperature for 30 min. The reaction mixture was then diluted with chloroform and washed with 1N NaOH. The organic layer was separated, dried over magnesium sulfate, filtered and concentrated in vacuo to afford the crude title compound (approximately 500 mg) which was used directly in Example 5.
