Compound 276 (53.0 mg, 94.7 μmol) was dissolved in THF (2 mL).). Tetrabutylammonium fluoride, 1.0M in THF (0.500 mL, 500 μmol) was added and the reaction was stirred at room temperature for 4.5 hours. The solvent was evaporated to give an orange oil. Preparative reverse phase HPLC (gradient elution 0.1% TFA in water/10-70% acetonitrile) afforded a yellow solid. This residue was added to aqueous NaHCO3 (saturated, 10 mL) and extracted with dichloromethane+10% methanol (3×30 mL). The combined organics were dried (MgSO4) and evaporated to give a yellow solid. This product was taken up in methanol (2 mL) and 1 mL methanol (saturated at room temperature with HCl) was added. 20 mL diethyl ether was added to precipitate the product, which was washed with ether and dried in vacuo to give compound 275 as yellow solid (21 mg, 50%). 1H NMR (500 MHz, DMSO-d6) δ 9.21 (s, 2 H) 8.56 (d, J=8.56 Hz, 2 H) 7.63 (d, J=2.69 Hz, 4 H) 7.44-7.57 (m, 2 H) 6.87 (d, J=8.56 Hz, 2 H) 5.43 (quin, J=8.62 Hz, 1 H) 4.47 (br. s., 1 H) 4.00 (s, 3 H) 3.09-3.21 (m, 1H) 2.00-2.22 (m, 5 H) 1.90-2.04 (m, 1 H) 1.66-1.85 (m, 2 H) ppm.
