Benzyl chloroformate → N-(4-{[(Benzyloxy)carbonyl]amino}-3-methylbenzoyl)threonine methyl ester

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Reaction Steps

10% Pd/C (1.2 g) was added to a solution of N-(3-methyl-4-nitrobenzoyl)threonine methyl ester obtained in Example (108a) (7.2 g, 24.3 mmol) in ethanol (40 mL), and the mixture was stirred in a hydrogen atmosphere at room temperature for one hour and 20 minutes. Pd/C was filtered off, and the filtrate was concentrated under reduced pressure. Water (20 mL), THF (20 mL), sodium bicarbonate (2.52 g, 30 mmol) and benzyl chloroformate (5.37 g, 30 mmol) were added to the resulting residue, and the mixture was stirred at room temperature for one hour. Following extraction with dichloromethane, the organic layer was washed with water, a 1 N aqueous hydrochloric acid solution and brine, dried over magnesium sulfate, and concentrated. Thereafter, the resulting residue was purified by silica gel column chromatography (elution solvent: chloroform/methanol=1/0, 95/5, 90/10, 85/15) to obtain 7.4 g of the title compound as a colorless solid (76%).

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