Reaction Steps
To a solution containing 66 (160 mg, 0.27 mmol) in DCM (3 mL) was added TFA (3 mL) at 0° C. After 1 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, 5-40% ACN/water containing 0.1% HOAc over 30 min; Flow: 40 mL/min) to afford 100 mg (38%, 3 steps) of 67. 1H NMR (300 MHz, CDCl3/d4-MeOH), mixture of amide rotamers: δ10.34 (br s, 0.1H), 9.76 (br s, 0.3H), 7.92 (br d, 0.3H), 7.55 (dd, J=8.9, 5.3 Hz, 0.7H), 7.38 (m, 0.3H), 7.35 (s, 0.3H), 7.25 (m, 0.3H), 7.22 (s, 0.7H), 7.02 (m, 1H), 6.82 (dt, J=9.2, 2.0 Hz, 0.7H), 5.11 (t, J=7.8 Hz, 0.7H), 4.79 (m, 0.3H), 4.30 (br s, 2H), 4.24 (m, 1.7H), 4.14 (m, 1.3H), 4.00 (m, 1H), 3.82 (m, 1H), 3.71 (m, 2H), 3.51 (q, J=6.9 Hz, 0.7H), 3.38 (m, 0.3H), 3.29 (m, 0.3H), 3.15 (app q, J=9.0 Hz, 0.7H), 3.01 (s, 0.7H), 2.98 (s, 2.3H), 2.44 (s, 2.3H), 2.34 (s, 0.7H), 2.20 (m, 0.7H), 2.00 (br s, 3.3H), 1.57 (m, 0.3H), 1.35 (d, J=6.9 Hz, 2.3H), 1.17 (d, J=6.9 Hz, 0.7H), 0.71 (m, 1.5H), 0.47 (m, 1.5H) ppm. 13C NMR (75 MHz, CDCl3/d4-MeOH), mixture of amide rotamers: δ176.6, 171.3, 171.2, 170.7, 170.5, 169.1, 161.6, 158.4, 136.2, 136.0, 135.9, 124.3, 122.9, 122.8, 122.7(2), 120.2, 120.1, 108.3, 108.1, 107.8, 97.6, 97.5, 97.2, 65.0, 64.9, 62.3, 57.9, 57.5, 55.4, 53.4, 52.3, 52.2, 51.7, 47.4, 46.8, 43.1, 38.5, 37.6, 34.4, 33.9, 33.2, 32.2, 32.0, 25.9, 24.2, 22.1, 17.1, 16.8, 10.0, 9.1 ppm. Mass spectrum, m/z [494.2] (M+H)+.
