N[C@H](C([NH:8][C@H:9]([C:14]([OH:16])=[O:15])[CH2:10][C:11]([OH:13])=[O:12])=O)C(C)C.CN1C2C(=CC=CC=2)C(C)=C1C(O)=O.CCN=C=NCCCN(C)C>CN(C=O)C.CN(C)C1C=CN=CC=1>[NH2:8][C@H:9]([C:14]([OH:16])=[O:15])[CH2:10][C:11]([OH:13])=[O:12]To a stirred turbid mixture of N-[valinyl]aspartic acid, α-methyl, β-tert-butyl diester 2.75 g, 9.11 mmol) and 1,3-dimethylindole-2-carboxylic acid (1.95 g, 10.3 mmol) in DMF (30 ml) was added 4-dimethylaminopyridine (DMAP) (1.26 g, 10.3 mmol) and EDAC (2.37 g, 12.4 mmol). The reaction mixture was stirred under a nitrogen atmosphere at 0° C. for 1 hour and at room temperature for 3 hours. The reaction mixture was then partitioned between ethyl acetate and 5% KHSO4 solution and the aqueous solution was back-extracted with ethyl acetate. The combined extracts were washed with saturated NaHCO3 solution, water, and brine, dried over sodium sulfate, and concentrated to give a solid. The solid was triturated with ether to give N-[1,3-dimethyl-indole-2-cabonyl)valinyl]aspartic acid, α-methyl, β-tert-butyl diester as a white powder (2.87 g, 67%).
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