In a 150 mL RBF was weighed 3-iodo-1-tosyl-1H-indole-5-carbohydrazide (1.16 g, 2.55 mmol) followed by THF (20 mL), isovalerianic acid (0.29 mL, 2.55 mmol) (TCI America) and N-ethyl-N-isopropylpropan-2-amine (1.11 mL, 6.37 mmol). To this stirring suspension was added HATU (1.07 g, 2.80 mmol) in one portion and the solution was stirred at RT for 2 h. The mixture was concentrated and treated with POCl3 (10 mL, 107 mmol) under argon. The flask was fitted with a reflux condenser and the reaction was heated to 110° C. for 14 h. The excess POCl3 was removed under reduced pressure and the crude residue was treated with EtOAc and a saturated solution of NaHCO3. It was extracted with EtOAc (50 mL) and washed with brine and dried over MgSO4, filtered and concentrated. The crude material was purified by flash chromatography (0-50% EtOAc in Hex) affording 2-(3-iodo-1-tosyl-1H-indol-5-yl)-5-isobutyl-1,3,4-oxadiazole (277 mg, 35%) as a white amorphous solid. MS (ESI, pos. ion) m/z: 522.0 (M+H)1. 1H NMR (400 MHz, DMSO-d6) δ ppm 8.24 (s, 1H), 8.17 (d, J=8.6 Hz, 1H), 8.03 (d, J=8.8 Hz, 1H), 7.97 (m, J=8.2 Hz, 2H), 7.87 (s, 1H), 7.43 (m, J=8.2 Hz, 2H), 2.84 (d, J=7.0 Hz, 2H), 2.33 (s, 3H), 2.15 (dt, J=13.5, 6.8 Hz, 1H), 0.99 (d, J=6.7 Hz, 6H).
