A solution of 3-cyano-N-{4-[4-(3-cyano-4-fluorophenyl)-5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl}-1,2,5-oxadiazol-3-yl]benzamide (30 mg, 72 μmol) in benzene (2 mL) at 0° C. was treated with phosphorus pentachloride (45 mg, 0.22 mmol) and stirred at 90° C. for 2 h. The reaction mixture was concentrated, diluted with ethanol (2.5 mL), treated with sodium cyanoborohydride (14 mg, 0.22 mmol), and stirred for 16 h. The reaction mixture was purified by preparative LCMS to give the intermediate 5-[3-{4-[(3-cyanobenzyl)amino]-1,2,5-oxadiazol-3-yl}-5-oxo-1,2,4-oxadiazol-4(5H)-yl]-2-fluorobenzonitrile. This material was diluted with ethanol (1 mL), treated with 2.0 M sodium hydroxide in water (0.2 mL), and stirred for 45 min. Purification of the crude reaction mixture by preparative HPLC gave the desired product (3 mg, 11%). LCMS for C18H13FN7O2 (M+H)+: m/z 378.0.
