1-Phenyl-1H-tetrazole-5-thiol sodium salt (25 g) was added to a solution of (2R,3R,7S)-7-(iodomethyl)-2,3-diphenyl-1,4-dioxaspiro[4.4]nonane (48.3 g, described in WO 2003095438) in acetone (500 mL), and the mixture was stirred at 60° C. for three hours. The solvent was evaporated from the reaction solution under reduced pressure. The residue was purified by silica gel column chromatography (hexane:ethyl acetate=4:1→1:1) to give 5-({[(2R,3R,7S)-2,3-diphenyl-1,4-dioxaspiro[4.4]non-7-yl]methyl}sulfanyl)-1-phenyl-1H-tetrazole (39.5 g) as a pale yellow oil.
