The product of Example 4 (3 g, 10 mmol) was dissolved in dichloromethane (10 ml), oxalyl chloride (2.6 ml, 30 mmol) was added dropwise, and it was reacted at room temperature for 1 hr, then the reaction solution was concentrated to give a pale yellow oil which was further dissolved in dichloromethane. And then the resulted solution was added dropwise to an ice-water bath cooled solution of dimethylamine hydrochloride (1.6 g, 20 mmol) and triethylamine (4.3 ml, 30 mmol) in dichloromethane, then the mixture was slowly warmed to room temperature to react for 1 hour. The pH thereof was adjusted to about 7 with 1N hydrochloric acid, then it was extracted with dichloromethane. The organic phases were combined, washed with saturated sodium bicarbonate solution and saturated brine, dried over anhydrous sodium sulfate, concentrated and recrystallized with petroleum ether and ethyl acetate to give a white solid 3.1 g, yield: 95%. 1HNMR (300 MHz, CDCl3): δ 7.3-7.5 (5H, m), 7.2 (1H, m), 6.7-6.8 (3H, m), 5.0 (2H, s), 2.8-2.9 (1H, m), 2.7-2.8 (1H, m), 2.6 (3H, s), 2.5 (3H, s), 1.8-1.9 (1H, m), 1.4-1.6 (1H, m), 1.1 (3H, d, J=6.2), 0.8 (3H, t, J=6.8, 14.1). ESI-MS: 326.4 (M+H).
