Reaction Steps
To a solution of the product of Example 18 (1.61 g, 2.60 mmol) in 1.2-dichloroethane (30 mL) stirring at 0° C. was added boron trichloride (10 ml, 117 mmol). The resulting dark purple solution was stirred overnight at ambient temperature in a sealed tube. After cooling the solution to 0° C., methanol (25 mL) was carefully added over a period of 30 minutes (caution, gas evolution). The solution was subsequently concentrated and the resulting material dissolved in 30% isopropanol/chloroform then washed with saturated sodium bicarbonate, brine, dried over anhydrous sodium sulfate, filtered, and concentrated. The crude material was purified by radial chromatography (methanol/chloroform gradient) to give 0.34 g (27%) of the desired product as a white foam: 1H-NMR (300 MHz, DMSO-d6) δ 9.45 (s, 1H), 9.36 (s, 1H), 7.72 (d, J=8.8 Hz, 1H), 7.62 (d, J=9.2 Hz, 1H), 7.28 (d, J=8.7 Hz, 1H), 7.00-7.10 (m, 2H), 6.80-6.90 (m, 2H), 6.70-6.80 (m, 4H), 5.45 (s, 1H), 4.84 (s, 1H), 4.25 (s, 2H), 3.90-4.05 (m, 2H), 2.75-2.90 (m, 2H), 2.50-2.65 (m, 4H), 1.60-1.80 (m, 4H); 13C-NMR (75 MHz, DMSO-d6) δ 203.32, 191.97, 188.16, 186.14, 185.95, 177.43, 173.46, 169.60, 167.74, 163.48, 162.30, 159.87, 158.14, 154.98, 152.43, 60.50, 56.25, 54.00, 45.05, 41.00, 37.50, 35.00, 30.05, 27.50, 26.00, 22.50, 20.00; Anal. Calc'd. for: C, 79.24; H, 6.65; N, 3.19. Found: C, 78.99; H, 6.51; N, 2.92; MS (FD) m/e 440 (M+); IR (KBr) 3382.61, 2964.00, 1610.77, 1509.49 cm−1.
