Concentrated hydrochloric acid (14.3 μL) and heptane (7 mL) were added to a 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 (79.77 mg) in 2-propanol (3 mL). A small amount of the crystals obtained in Example 5 were added as seed crystals with stirring at room temperature. The mixture was transferred to a low temperature laboratory at about 5° C. and stirred for one hour. Thereafter, 1 mL of heptane was further added, followed by stirring for several minutes. When the precipitated solid was collected by filtration through a glass filter, the solid was precipitated in the filtrate. The precipitated solid was collected by filtration through a glass filter and dried under reduced pressure at room temperature to obtain 38.02 mg of the title compound as white solid crystals.
