Synthesis of Protected Amino Acid Derivative

Example 124

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HATU (39.9 g, 105 mmol) was added to a solution of 4-(((benzyloxy)carbonyl)amino) butanoic acid (26.1 g, 110 mmol) in DMF (300 mL). After stirring at r.t. for 30 min, the mixture was added to a solution of compound 110 (39.4 g, 100 mmol) and TEA (20.2 g, 200 mmol) in DMF (300 mL). The resulting mixture was stirred at r.t. for 2 h. Water was then added, extracted with EtOAc, the organic layer was washed with brine, dried over Na₂SO₄. Purification by column chromatography (20% to 70% EA/PE) yielded the title product as a white solid (45 g, 73% yield). ESI m/z calcd for C₃₃H₄₈N₃O₈ [M+H]⁺: 614.34, found 614.15.