[NH:1]1[C:9]2[C:4](=[CH:5][CH:6]=[CH:7][CH:8]=2)[CH2:3][CH:2]1[C:10]([OH:12])=[O:11].[CH2:13](O)[CH3:14].Cl.C(=O)([O-])[O-].[K+].[K+]>O1CCOCC1>[NH:1]1[C:9]2[C:4](=[CH:5][CH:6]=[CH:7][CH:8]=2)[CH2:3][CH:2]1[C:10]([O:12][CH2:13][CH3:14])=[O:11]A mixture of 25.2 g of indoline-2-carboxylic acid, 50 ml of ethanol and 200 ml of a 4N solution of hydrogen chloride in dioxane was stirred at room temperature for 3 days. At the end of this time, the reaction mixture was poured into an aqueous solution of potassium carbonate, after which it was extracted with ethyl acetate. The extract was washed with an aqueous solution of sodium chloride and dried over anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure, and the residue thus obtained was purified by column chromatography through silica gel, using a 2:1 by volume mixture of hexane and ethyl acetate as the eluent, to give 28.1 g of the title compound having Rf=0.81 (on silica gel thin layer chromatography using a 2:1 by volume mixture of hexane and ethyl acetate as the developing solvent).
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