Reaction Steps
To a solution of Compound 20b (37 mg, 0.13 mmol), DCC (26.7 mg, 0.13 mmol), and DMAP (31.6 mg, 0.26 mmol) in dry CH2Cl2 (20 mL) cooled in an ice-water bath was added methoxyacetic acid (17.5 mg, 0.19 mmol) followed by stirring at room temperature for 2 hours. The reaction mixture was filtered through a short plug of Celite with rinsing by EtOAc. The filtrate was concentrated under reduced pressure and the residue was purified by flash column chromatography (silica gel, 20 percent EtOAc in hexane) to give 30.1 mg (65 percent) of Compound 30b: pale yellow oil; Rf=0.38 (20 percent EtOAc in hexane); IR (neat) 2932, 2239,2229, 1756, 1182, 1126 cm−1; 1H NMR (300 MHz, CDCl3) δ8.32 (d, J=7.29 Hz, 1H), 8.14-8.00 (m, 1H), 7.92-7.81 (m, 2H), 7.58-7.44 (m, 3H), 7.50 (s, 1H), 6.33 (t, J=1.05 Hz, 1H), 4.15 and 4.13 (AB q, J=16.50 Hz, 2H), 3.48 (s, 3H), 2.55-2.20 (m, 4H), 2.00-1.60 (m, 4H); 13C NMR (75 MHz, CDCl3) δ170.4, 134.2, 133.4, 132.8, 132.2, 129.8, 129.3, 127.1, 127.0, 126.5, 125.9, 124.1, 123.3, 103.5, 94.4, 80.8, 79.0, 70.6, 70.2, 60.1, 28.2, 28.1, 22.5, 21.4; MS (+CI) m/z (relative intensity) 359 (M+H+, 4), 269 (100); HRMS (+EI) calcd for C24H22O3 (M+) 358.1569, found 358.1574.
