compound in an appropriate solvent adding a dialkyl azodicarboxylate thereto and allowing the reaction to proceed for 1 to 2 hours at 0 to 25 u00b0 c wherein the benzimidazole derivative of formula v may be used in a 1 to 1 2 equimolar amount based on the hydroxymethylpyridine derivative this procedure gives a high yield 95 or higher of the compound of formula ii the reaction pathway involved in step a is shown in scheme 4 wherein triphenylphosphine ph 3 p represents the phosphine compound wherein r and r u2032 are each independently a c 1 5 alkyl group and r is 3 methyl 4 2 2 2 trifluoroethoxy 2 pyridyl the organic solvent used in step a of the present invention may be selected from the group consisting of chloroalkanes e g dichloromethane chloroform and 1 2 dichloroethane aromatic hydrocarbons e g benzene tolueneandxylene ethers e g tetrahydrofuran diisopropylether methyl t butylether and dioxane ketones e g methylisobutylketone nitrites e g acetonitrile amides e g dimethylacetamide and dimethylformamide and a mixture thereof the phosphine compound which can be used in the present invention includes triethylphosphine trimethylphosphine tributylphosphine and triphenylphosphine among which triphenylphosphine is preferred the phosphine compound may be used in a 1 to 1 5 molar amount preferably 1 1 mole based on a mole of the compound of formula iii further the dialkyl azodicarboxylate which can be used in the present invention includes diisopropyl azodicarboxylate or diethyl azodicarboxylate dead the dialkyl azodicarboxylic acid may be used in a 1 to 1.