Carbonyl diimidazole (CDI) (2.3 g, 14.24 mmol) was added to a stirred solution of 2-acetoxyacetic acid (1.68 g, 14.24 mmol) in NMP (10 mL). After 30 minutes, 6-bromo-N-(5-(N-hydroxycarbamimidoyl)-2-methylphenyl)imidazo[1,2-a]pyridine-3-carboxamide (50f) (1.38 g, 3.56 mmol) was added in one portion and the resulting solution was stirred for 30 minutes before it was heated at 125° C. for 15 minutes in a microwave reactor. The reaction solution was subjected to standard aqueous work up to afford a residue which was hydrolyzed by lithium hydroxide monohydrate (897 mg, 21.36 mmol) in THF/MeOH/H2O (3:2:1). After removal of all solvents 2M NaHCO3 (10 mL) was added. The precipitate was filtered and dried in air to afford 6-bromo-N-(5-(5-(hydroxymethyl)-1,2,4-oxadiazol-3-yl)-2-methylphenyl)imidazo[1,2-a]pyridine-3-carboxamide (142). 1H NMR (400 MHz, d6-DMSO) δ 10.14 (s, 1H), 9.64 (d, J=1.2 Hz, 1H), 8.60 (s, 1H), 8.11 (d, J=1.6 Hz, 1H), 7.83 (dd, J=1.6, 8.0 Hz, 1H), 7.79 (dd, J=0.8, 9.6 Hz, 1H), 7.67 (dd, J=2.0, 9.6 Hz, 1H), 7.51 (d, J=8.0 Hz, 1H), 6.09 (s, 1H), 4.81 (s, 2H), 2.37 (s, 3H). MS m/z 427.9, 429.9 (M+1)+.
