A solution of phosphoric acid (13.2 mg) in ethanol (0.05 mL) was added to a mixed solution of (8S)-2-{(E)-2-[6-methoxy-5-(4-methyl-1H-imidazol-1-yl)pyridin-2-yl]vinyl}-8-(2-trifluoromethylphenyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[1,5-a]pyridine (50 mg) in heptane (0.6 mL)-ethanol (0.15 mL) at room temperature. The reaction solution was stirred at room temperature, and the precipitated solid was collected by filtration through a glass filter. The solid was washed with heptane-ethanol (3:1) and then dried under reduced pressure at room temperature to obtain 37.6 mg of the title compound as white solid crystals.
