Step D: Synthesis of ethyl 5-methoxy-2-methylbenzoate as an intermediate; sodium hydride (60% dispersed in mineral oil, 1.50 g, 37.4 mmol) was suspended in N,N-dimethylformamide (50 mL) under nitrogen protection and stirred for 10 min. Subsequently, a solution of ethyl 5-hydroxy-2-methylbenzoate (5.18 g, 28.7 mmol) in N,N-dimethylformamide (100 mL) was slowly added dropwise. After the dropwise addition was completed, stirring of the reaction mixture was continued for 3 hours at room temperature. Next, iodomethane (2.69 mL, 43.1 mmol) was added and the reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the mixture was poured into water (200 mL) and extracted with ethyl acetate (200 mL). The organic phase was washed sequentially with 5% aqueous lithium chloride (200 mL), water (200 mL) and brine (100 mL), dried over anhydrous magnesium sulfate and concentrated under reduced pressure. Purification by fast column chromatography (silica gel, ethyl acetate/hexane=1:19) afforded ethyl 5-methoxy-2-methylbenzoate (4.18 g, 75% yield) as a colorless oily liquid.1H NMR (300 MHz, CDCl3) δ 7.44 (d, J=2.7 Hz, 1H), 7.14 (d, J=8.4 Hz, 1H), 6.95 ( dd, J=2.7,8.4Hz, 1H), 4.35 (q, J=7.2Hz, 2H), 3.82 (s, 3H), 2.51 (s, 3H), 1.39 (t, J=7.2Hz, 3H).
