1,1′-Carbonyldiimidazole (24.8 mg) was added to a solution of 3-(6-{(E)-1-(4-tert-butylphenyl)-2-[(2R)-1-(2,4-dimethoxybenzyl)-5-oxopyrrolidin-2-yl]ethenyl}-2-oxo-1,2-dihydropyridin-3-yl)propanoic acid (77.8 mg) in tetrahydrofuran (1.6 mL). 28% aqueous ammonia (0.2 mL) was further added, followed by stirring for 15 hours. The reaction system was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (chloroform:methanol=10:0→9:1) to give 3-(6-{(E)-1-(4-tert-butylphenyl)-2-[(2R)-1-(2,4-dimethoxybenzyl)-5-oxopyrrolidin-2-yl]ethenyl}-2-oxo-1,2-dihydropyridin-3-yl)propanamide as a colorless amorphous (82.6 mg).
