To a flask containing tert-butyl 5-(5-(3-cyano-4-isopropoxyphenyl)-1,2,4-oxadiazol-3-yl)-1H-indole-1-carboxylate INT-67 (75 mg, 0.17 mmol) was added dioxane (2 mL) followed by 4N HCl in dioxane (0.5 mL, 2 mmol). The reaction mixture was stirred overnight at room temperature then heated at 50° C. overnight. Additional 4N HCl/dioxane (0.5 mL, 2 mmol) was added and the mixture was heated at 50° C. for an additional 2 h to complete the deprotection. The reaction mixture was diluted with EtOAc and washed with NaHCO3. The combined organic layers were washed with brine, dried over Na2SO4, and concentrated. The material was purified by chromatography (EtOAc/hexanes) to provide 17 mg (30%) of 5-(3-(1H-indol-5-yl)-1,2,4-oxadiazol-5-yl)-2-isopropoxybenzonitrile 68 as a white solid. LCMS-ESI (m/z) calculated for C20H16N4O2: 344.5; found 345.1 [M+H]+, tR=2.34 min (Method 1). 1H NMR (400 MHz, CDCl3) δ 8.51-8.47 (m, 1H), 8.45 (d, J=2.2 Hz, 1H), 8.38 (d, J=7.2 Hz, 1H), 8.35 (dd, J=8.9, 2.2 Hz, 1H), 7.99 (dd, J=8.5, 1.6 Hz, 1H), 7.51 (d, J=8.5 Hz, 1H), 7.33-7.28 (m, 1H), 7.11 (d, J=9.0 Hz, 1H), 6.72-6.64 (m, 1H), 4.79 (dt, J=12.2, 6.1 Hz, 1H), 1.47 (t, J=5.8 Hz, 6H).
