Ammonium Chloride → (S)-methyl 2-((tert-butoxycarbonyl)amino)-3-(4-carbamoyl-2,6-dimethylphenyl)propanoate

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Reaction Steps

Into a stirring solution of (S)-4-(2-tert-butoxycarbonylamino-2-methoxycarbonylethyl)-3,5-dimethylbenzoic acid (3.00 g, 8.54 mmol), PyBOP (6.68 g, 12.8 mmol) and HOBt (1.74 g, 12.8 mmol) in DMF (36 mL) was added DIPEA (5.96 mL, 34.2 mmol) and NH4Cl (0.92 g, 17.1 mmol). The resulting mixture was stirred at rt for 40 min before being partitioned between aqueous NH4Cl solution and EtOAc. The separated organic phase was washed sequentially with 2N citric acid aqueous solution, saturated aqueous NaHCO3 solution, and brine, then dried over Na2SO4 overnight. After filtration and concentration, the residue was purified by flash column chromatography (eluent: EtOAc) to give the product. (3.00 g, 100%); 1H NMR (300 MHz, CDCl3): δ 1.36 (9H, s), 2.39 (6H, s), 3.11 (2H, J=7.2 Hz), 3.65 (3H, s), 4.53-4.56 (1H, m), 5.12 (1H, d, J=8.7 Hz), 5.65 (1H, br s), 6.09 (1H, br s), 7.46 (2H, s); MS (ES+) (relative intensity): 250.9 (100) (M-Boc)+.

Provenance & Evidence