Methanol → Methyl 3-[5-(2-aminopyridin-4-yl)-2-ethyl-1,3-thiazol-4-yl]benzoate

To a solution of 3-[5-(2-amino-4-pyridyl)-4-(3-cyanophenyl)-2-ethyl-1,3-thiazol-4-yl]benzoic acid (0.3 g, 1.0 mmol) in methanol (10 mL) was added concentrated sulfuric acid (0.1 mL) and the mixture was stirred for 5 hours at 70° C. The reaction mixture was basified with sodium hydroxide solution and extracted with ethyl acetate. The extracts were washed with water, then, dried and concentrated. The residue was washed with hexane-ethyl acetate to obtain a title compound (0.29 g, yield 85%).