A mixture of 2-butyl-1-[(2'-cyanobiphenyl-4-yl)methyl]-7-methylbenzimidazole (0,5 g), sodium azide (1.3 g) and ammonium chloride (1.1 g) in DMF (5 ml) was stirred for 3.5 days at 110-120° C. To the reaction mixture was added water, which was made acidic (pH 3-4) with 1N-HCl, followed by extraction with ethyl acetate. The organic layer was washed with water and dried. The solvent was distilled off, and the residue was purified by column chromatography on silica gel to give crystals. Recrystallization from ethyl acetate-methanol afforded colorless crystals (0.36 g, 62%),
