[C:1]([N:4]1[C:12]2[C:7](=[CH:8][C:9]([O:15][CH3:16])=[C:10]([O:13][CH3:14])[CH:11]=2)[CH2:6][C:5]1=[O:17])(=[O:3])[CH3:2].[CH3:18][CH2:19][O:20][C:21](OCC)(OCC)[C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1>C(OC(=O)C)(=O)C>[C:1]([N:4]1[C:12]2[C:7](=[CH:8][C:9]([O:15][CH3:16])=[C:10]([O:13][CH3:14])[CH:11]=2)[C:6](=[C:21]([O:20][CH2:19][CH3:18])[C:22]2[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=2)[C:5]1=[O:17])(=[O:3])[CH3:2]10.0 g of 1-acetyl-5,6-dimethoxy-2-indolinone, 29.2 ml of triethyl orthobenzoate and 100 ml of acetic anhydride are stirred for 48 hours at 120° C. The solvent is eliminated and the residue evaporated with toluene, combined with ether and the precipitate formed (starting compounds is suction filtered. The filtrate is concentrated by evaporation and separated through a silica gel column with toluene, then with toluene/ethyl acetate (10:1). The product is triturated with ether, suction filtered and dried in vacuo at 100° C.
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