Reaction Steps
To a solution containing 74 (202 mg, 0.33 mmol) in DCM (10 mL) was added TFA (4 mL) at 0° C. After 2 h, the reaction mixture was concentrated in vacuo. The residue was dissolved in EtOAc and the resultant organic solution was washed successively with saturated aqueous NaHCO3 and brine, dried over anhydrous Na2SO4, filtered, and concentrated. The crude product was purified by RP-HPLC (2″ Dynamax C18, 10-70% ACN/water containing 0.1% HOAc over 30 min; Flow: 40 mL/min) to afford 125 mg (61%, 3 steps) of 75. 1H NMR (CDCl3, 300 MHz): δ8.37 (dd, J=6.0, 10.5 Hz, 2H), 8.19 (s, 1H), 8.11 (dd, J=5.4, 8.7 Hz, 1H), 7.82 (d, J=8.7 Hz, 1H), 6.99-6.88 (m, 2H), 6.74-6.68 (m 1H), 6.62-6.58 (m, 1H), 4.74-4.60 (m, 1H), 4.48-4.44 (m, 1H) 4.16-4.04 (m, 2H), 3.69 (dd, J=6.0, 11.4 Hz, 1H), 3.51-3.42 (m, 1H), 3.26 (dd, J=6.6, 13.5 Hz, 1H), 2.76 (br s, 4H), 2.53-2.47 (m, 1H), 2.44-2.39 (m, 3H), 2.21-2.01 (m, 3H), 1.39-1.32 (m, 3H), 1.06-0.96 (m, 6H) ppm. 13C NMR (CDCl3, 75 MHz) δ173.9, 170.8, 160.2 (JCF=237.4 Hz), 159.8, 136.2, 123.4, 120.9 (JCF=10.1 Hz), 116.6, 110.1, 108.5 (JCF=24.5 Hz), 97.2 (JCF=26.2 Hz), 68.2, 60.3, 59.7, 55.9, 51.4, 47.2, 38.9, 34.2, 31.5, 30.7, 19.4, 18.8, 18.0 ppm. Mass spectrum, m/z [508.3] (M)+.
