C([O:3][C:4](=[O:35])[CH2:5][CH2:6][C:7]1[CH:8]=[C:9]2[C:13](=[CH:14][CH:15]=1)[NH:12][C:11]([C:16](=[O:34])[NH:17][CH2:18][CH2:19][CH2:20][CH2:21][CH2:22][CH2:23][C:24](=[O:33])[NH:25][O:26][CH:27]1[CH2:32][CH2:31][CH2:30][CH2:29][O:28]1)=[CH:10]2)C.[OH-].[Na+].Cl>C1COCC1.CO>[O:28]1[CH2:29][CH2:30][CH2:31][CH2:32][CH:27]1[O:26][NH:25][C:24]([CH2:23][CH2:22][CH2:21][CH2:20][CH2:19][CH2:18][NH:17][C:16]([C:11]1[NH:12][C:13]2[C:9]([CH:10]=1)=[CH:8][C:7]([CH2:6][CH2:5][C:4]([OH:35])=[O:3])=[CH:15][CH:14]=2)=[O:34])=[O:33]3-{2-[6-(Tetrahydro-pyran-2-yloxycarbamoyl)-hexylcarbamoyl]-1H-indol-5-yl}-propionic acid ethyl ester (550 mg, 1.13 mmol) was dissolved in THF/methanol (50 ml/25 ml). 1.4 M NaOH solution (50 ml) was added and the reaction stirred at room temperature for 4 h. The solvent was reduced to ˜50% volume and 1M HCl added to pH 6-7. The mixture was extracted with DCM and further extracted with EtOAc. The combined organic layer was dried, Na2SO4 and the solvent removed in vacuo to give the required product 357 mg (69% yield) as a yellow powder which was used in the next step without further purification. LCMS purity 94%, m/z 460 [M++H]+
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