To a suspension of 2,4-dimethylthiazole-5-carboxylic acid (236 mg, 1.5 mmol) in THF (12 mL) was added dropwise n-BuLi (1.6 M in hexanes, 1.88 mL, 3.0 mmol) under Ar at −75° C. The brown suspension was stirred at −75° C. for 2 h and then a solution of 5-(4-fluoro-phenyl)-3-methyl-3H-[1,2,3]triazole-4-carbaldehyde (308 mg, 1.50 mmol) in THF (4.5 mL) was added at −75° C. and the brown suspension was stirred at −75° C. for 2 h. The mixture was then quenched with an aqueous solution of citric acid (5%, 15 mL), allowed to warm to room temperature. The mixture was then poured into saturated ammonium chloride solution and extracted with ethyl acetate and the combined organic extracts washed with brine, dried over sodium sulphate, filtered and evaporated. Purification by chromatography (silica, 0 to 30% methanol in dichloromethane) afforded 2-{2-[5-(4-fluoro-phenyl)-3-methyl-3H-[1,2,3]triazol-4-yl]-2-hydroxy-ethyl}-4-methyl-thiazole-5-carboxylic acid (417 mg, 77%) as a yellow foam. The acid was then dissolved in methanol (4 mL) and diethylether (2 mL) and trimethylsilyldiazomethane (2M in diethylether, 5×0.38 mL, 3.75 mmol) added dropwise. The reaction was quenched with a few drops of AcOH and evaporated. To the brown oil was added sodium hydroxide (1 N, 20 mL) and extracted with ethyl acetate. The combined organic layers were washed with brine, dried over sodium sulfate and evaporated. Purification by chromatography (silica, 0 to 30% methanol in dichloromethane) afforded the title compound (214 mg, 38%) as a light brown foam.
