Sodium Hydroxide → Biphenyl-2-ylcarbamic Acid 1-(2-{[4-(4-[{(R)-2-(tert-butyldimethyl-silanyloxy)-2-(8-hydroxy-2-oxo-1,2-dihydroquinolin-5-yl)-ethylamino]methyl}-2,5-dimethylphenylcarbamoyl)butyl]methylcarbamoyl}ethyl)piperidin-4-yl Ester

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Reaction Steps

To the stirred solution of biphenyl-2-ylcarbamic acid 1-(2-{[4-(4-formyl-2,5-dimethylphenylcarbamoyl)butyl]methylcarbamoyl}ethyl)piperidin-4-yl ester (0.748 mmol) in DCM from the previous reaction was added 5-[(R)-2-amino-1-(tert-butyl-dimethylsilanyloxy)ethyl]-8-hydroxy-1H-quinolin-2-one acetic acid salt (0.295 g, 0.748 mmol) in 1:1 MeOH:DCM (3.0 mL). The resulting mixture was stirred at room temperature for 30 min and then sodium triacetoxyborohydride (0.476 g, 2.24 mmol) was added and stirring was continued at room temperature for 4 h. Aqueous NaOH (1 M, 3 mL) and DCM (3 mL) were added and the layers were separated. The organic layer was dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel flash chromatography (0-15% MeOH in DCM) to give the title compound (420 mg, 60% yield) as a yellow solid.

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