Prepared using General Procedure 2. A flask containing 3-cyano-4-isopropoxybenzoic acid (135 mg, 0.66 mmol), HOBt (130 mg, 0.85 mmol) and EDC (164 mg, 0.85 mmol) in DMF (2.5 mL) was stirred for 1.5 h at room temperature under an atmosphere of N2. A solution of crude tert-butyl 5-(N-hydroxycarbamimidoyl)-1H-indole-1-carboxylate INT-66 (199 mg, 0.72 mmol) in DMF (2.5 mL) was added to the mixture. After 1 h at room temperature, the mixture was heated to 75° C. and stirred overnight. The reaction mixture was diluted with NaHCO3 and extracted with EtOAc. The combined organic extracts were dried over Na2SO4 and concentrated. The resulting crude material was chromatographed (EtOAc/hexanes) to provide 174 mg (59%) of tert-butyl 5-(5-(3-cyano-4-isopropoxyphenyl)-1,2,4-oxadiazol-3-yl)-1H-indole-1-carboxylate INT-67 as a white solid. LCMS-ESI (m/z) calculated for C25H24N4O4: 444.5; found 445.1 [M+H]+, tR=3.67 min (Method 1).
