[H-].[Na+].[CH3:3][O:4][C:5]([C:7]1[C:15]2[C:10](=[CH:11][CH:12]=[CH:13][CH:14]=2)[NH:9][CH:8]=1)=[O:6].[CH2:16](I)[CH3:17].O.[CH2:20]1COCC1>CCOC(C)=O>[CH2:3]([O:4][C:5]([C:7]1[C:15]2[C:10](=[CH:11][CH:12]=[CH:13][CH:14]=2)[N:9]([CH2:16][CH3:17])[CH:8]=1)=[O:6])[CH3:20]To a suspension of NaH (50-60% dispersion in mineral oil, 548.0 mg, 11.4 mmol, 2.0 eq) in THF (20 mL), 1H-indole-3-carboxylic acid methyl ester (1.0 g, 5.7 mmol, 1.0 eq) was added and after 20 min also ethyl iodide (507.0 μL, 6.3 mmol, 1.1. eq) was added. The reaction was heated at 70° C. for 1 h. The mixture was cooled down to 0° C. and water (10 mL) was added carefully. AcOEt was added and the organic phase was collected and concentrated, to give the crude compound that was purified through SiO2 column (10 g) with gradient elution from 100% cyclohexane to cyclohexane-EtOAc 80:20. The title product (860 mg, 74% yield) was obtained.
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