Nitric acid (65% solution, 0.20 mL, 3.2 mmol) was added to a solution of Example 1C (1.0 g, 3.2 mmol) in acetic acid (5 mL) at room temperature. The solution was stirred for 3 hours, and then the reaction mixture was poured into water (200 mL). The precipitate was collected by filtration from the aqueous solution to afford the title compound. 1H NMR (300 MHz, DMSO-d6) d ppm 8.00 (dd, J=8.92, 2.58 Hz, 1H), 7.79 (d, J=2.78 Hz, 1H), 7.24 (d, J=9.12 Hz, 1H), 3.86-4.10 (m, 2H), 3.36-3.50 (m, 1H), 3.20-3.29 (m, 1H), 2.81-2.99 (m, 1H), 2.62-2.77 (m, 1H), 2.18 (d, J=13.48 Hz, 1H); MS (APCI+) m/z 307 (M+H-tBu)+.
