Reaction Steps
A brown solution of Intermediate 77d (135 mg, 0.168 mmol) and TBAF (1M in THF, 0.184 mL, 0.184 mmol) in THF (3 mL) was stirred at RT for 1 h. The solution was concentrated in vacuo, suspended in water (10 mL) and extracted with EtOAc-MeOH (19:1, 2×10 mL). The combined organics were washed with brine (10 mL), dried (Na2SO4), filtered and concentrated in vacuo to leave a brown solid. FCC, using 5-9% MeOH in DCM, gave a pale brown solid. Further purification by HPLC (XBridge C18 column, 25-75% MeCN in H2O, 0.1% NH4OH) gave the title compound as a white powder after freeze-drying (63.9 mg, 59%). LCMS (Method 5): Rt 4.33 min, m/z 649 [MH+]. 1H NMR (400 MHz, d6-DMSO): 1.27 (9H, s), 1.29-1.35 (1H, m), 1.71-1.77 (3H, m), 1.82-1.96 (3H, m), 2.01-2.17 (2H, m), 2.36 (3H, s), 3.02-3.07 (2H, m), 3.20 (1H, dd, J 11.9, 3.3), 3.25-3.28 (1H, m), 3.42 (1H, dt, J 10.5, 5.0), 3.52-3.58 (1H, m), 4.69 (1H, t, J 5.1), 4.81 (1H, td, J 8.6, 5.4), 5.48 (1H, t, J 4.3), 6.32 (1H, s), 7.09 (1H, d, J 8.3), 7.12 (1H, dd, J 9.9, 2.1), 7.27-7.39 (8H, m), 7.60 (1H, d, J 9.9), 7.80 (1H, d, J 2.1), 8.04 (1H, s).
