(Diazomethyl)trimethylsilane (0.6M hexane solution) (0.404 mL, 0.24 mmol) was added to a mixture of cis-3-(((5R)-5-((7-fluoro-1,1-dimethyl-2,3-dihydro-1H-inden-5-yl)carbamoyl)-2-methoxy-7,8-dihydro-1,6-naphthyridin-6 (5H)-yl)carbonyl)cyclobutanecarboxylic acid (60 mg, 0.12 mmol) in THF (1 mL) and MeOH (1 mL) at 5° C., and the mixture was stirred at room temperature for 2 hr. To the reaction mixture were added water and ethyl acetate, the organic layer was separated, and the aqueous layer was extracted with ethyl acetate. The organic layer was washed with brine, and dried over magnesium sulfate, and the solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography (solvent gradient; 5→50% ethyl acetate/hexane) to give the title compound (50 mg, 0.098 mmol, 81%) as a colorless oil.
