Nitration and Acetylation of Compound 101

Example 40

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To a solution of compound 101 (5.96 g, 35.9 mmol, 1.0 eq.) in anhydrous dichloromethane (200 mL) was added Ac₂O (3.2 mL, 33.9 mmol, 2.0 eq.) and HNO₃ (65%-68%, 3.5 mL, 50.79 mmol, 3.0 eq.) at room temperature. The mixture was stirred at room temperature for 30 min, and TLC analysis showed that the reaction was completed. The reaction solution was washed with water (3×200 mL), and the aqueous layer was back-extracted with dichloromethane (3×100 mL). The combined dichloromethane solution was washed with brine, dried over anhydrous Na₂SO₄, filtered, concentrated and purified by SiO₂ column chromatography (5:1 hexanes/EtOAc) to give compound 102 as a yellow solid (4.18 g, 72% yield). ¹H NMR (500 MHz, CDCl₃) δ 10.49 (s, 1H), 7.89 (s, 1H), 7.44 (d, J=8.4 Hz, 1H), 7.09 (d, J=8.6 Hz, 1H), 4.32 (d, J=8.3 Hz, 1H), 4.12 (dd, J=14.0, 7.0 Hz, 2H), 3.80 (s, 1H), 2.76 (dd, J=13.0, 6.8 Hz, 2H), 2.59 (s, 1H), 1.88 (s, 1H), 1.37 (t, J=8.7 Hz, 9H), 1.25 (dd, J=13.5, 6.9 Hz, 4H), 1.16 (t, J=8.0 Hz, 3H). MS ESI m/z calcd for C₁₉H₂₈NaN₂O₇ [M+Na]⁺ 419.19, found 419.17.