To a solution of 2-benzoylamino-4-methylthiazole-5-carboxylic acid (0.13 g, 0.50 mmol) and 4-methylmorpholine (0.08 mL, 0.70 mmol) in tetrahydrofuran (20 mL) at 0° C. was added iso-butylchloroformate (0.08 mL, 0.60 mmol). The reaction mixture was stirred for 15 minutes, then warmed to ambient temperature and stirred for another hour before α-ethylbenzylamine (0.1 mL, 0.70 mmol) was added. The reaction mixture was kept stirring at ambient temperature overnight and then concentrated. Purification of the residue by column chromatography afforded the title compound in 19% yield (0.037 g); m. p. 87-89° C.; 1H NMR (CDCl3, 300 MHz) δ 7.89-7.86 (m, 2H), 7.61-7.22 (m, 8H), 5.91 (d, J=7.5 Hz, 1H), 5.02-4.94 (m, 1H), 2.33 (s, 3H), 2.27-1.78 (m, 2H), 0.92 (t, J=7.5 Hz, 3H); 13C NMR (CDCl3, 75 MHz) δ 165.1, 161.4, 157.0, 152.1, 141.8, 133.3, 131.4, 129.1, 128.7, 127.6, 127.5, 126.6, 118.8, 55.6, 29.3, 16.7, 10.8. MS (ES+) m/z 380.5 (M+1).
