T3P (8.24 mL, 14.00 mmol) was added to a mixture of 2-(tert-butoxycarbonyl)-6-(methoxymethyl)-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid (1.5 g, 4.67 mmol), 7-fluoro-1,1-dimethyl-2,3-dihydro-1H-inden-5-amine (0.837 g, 4.67 mmol), DIEA (4.08 mL, 23.34 mmol), DMAP (0.570 g, 4.67 mmol) and ethyl acetate (5 mL) at 60° C., and the mixture was stirred at 60° C. for 2 days. To the reaction mixture was added ethyl acetate, and the mixture was washed with water and 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; 32→40% ethyl acetate/hexane) to give tert-butyl 1-((7-fluoro-1,1-dimethyl-2,3-dihydro-1H-inden-5-yl)carbamoyl)-6-(methoxymethyl)-3,4-dihydroisoquinoline-2 (1H)-carboxylate (1.600 g, 3.32 mmol, 71.0%) as a white solid.
