A mixture of 2-(4-methylthiazol-5-yl)benzoxazole-4-carboxylic acid (60 mg, 0.23 mmol), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (88 mg, 0.46 mmol), 1-hydroxybenzotriazole (62 mg, 0.46 mmol) and 3-amino-9-methyl-9-azabicyclo[3.3.1]nonane dihydrochloride (65 mg, 0.29 mmol) in DMF (5 mL) was stirred at room temperature for 10 min, then triethylamine (0.29 mL, 2.11 mmol) was added. The resulting reaction mixture was stirred at room temperature overnight. The mixture was diluted with ethyl acetate and then washed with a saturated solution of sodium bicarbonate. The aqueous layer was further extracted with ethyl acetate (2×100 mL). The combined organic layers were washed with brine (2×100 mL), dried (Na2SO4), filtered and concentrated. The crude material was purified by column chromatography (silica gel, 90:9:1 dichloromethane/methanol/concentrated ammonium hydroxide) and recrystallization from acetonitrile to afford the desired product (57 mg, 63%) as a light yellow solid: 1H NMR (300 MHz, CDCl3) δ 8.92 (br s, 1H), 8.90 (s, 1H), 8.22 (dd, J=7.8, 1.0 Hz, 1H), 7.69 (dd, J=8.1, 1.0 Hz, 1H), 7.48 (t, J=8.0 Hz, 1H), 4.70-4.57 (m, 1H), 3.25-3.10 (m, 2H), 3.10 (s, 3H), 2.75-2.60 (m, 2H), 2.57 (s, 3H), 2.15-1.95 (m, 3H), 1.65-1.45 (m, 3H), 1.25-1.10 (m, 2H); MS (ESI+) m/z 397 (M+H).
