7.9 mg of 2-hydroxypyridine (0.08 mmol) was added to a solution of 200 mg of {(S)-2-[4-(2,6-difluorophenyl)-2,2-dimethyl-5-oxopiperazin-1-yl]-1-[(2S,4R)-4-methyl-5-oxotetrahydrofuran-2-yl]ethyl}carbamic acid t-butyl ester obtained in Example (93b) (0.41 mmol) in cyclohexylamine (1.0 ml), and the mixture was stirred at 80° C. for three hours. The reaction mixture was cooled and then water was added, followed by extraction with methylene chloride. Then, the organic layer was dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (elution solvent:methylene chloride/methanol=20/1) to obtain 218 mg of the title compound (yield: 88%).
