Diisopropylethylamine → ethyl (R) 3-[4-(2-{4-[(2,3-dihydro-indole-1-carbonyl)-amino]-3-methoxy-phenyl}-acetylamino)-phenyl]-butyrate

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A solution of ethyl (R) 3-(4-aminophenyl)butyrate (790 mg), 4-[(2,3-dihydro-indole-1-carbonyl)-amino]-3-methoxy-phenyl-acetic acid (1.24 g, Reference Example 5) and O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (1.45 g) in dimethylformamide (20 mL) was treated in one portion with diisopropylethylamine (1.4 mL). The resulting mixture was stirred at room temperature for 2 hours then poured into water (100 mL) and then extracted three times with ethyl acetate (50 mL). The combined extracts were washed with hydrochloric acid (0.5M), then with sodium hydrogen carbonate solution, then dried and then evaporated. The residue was triturated with a mixture of ethyl acetate and petrol to give the title compound (1.7 g) as a pink/orange powder. HPLC: RT=18.9 minutes (86% by ELS).

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