[CH3:1][O:2][C:3]1[C:8]2[O:9][C:10]3[CH:15]=[CH:14][CH:13]=[CH:12][C:11]=3[C:7]=2[C:6]([C:16]2([C:28]#[N:29])[CH2:25][CH2:24][C:23]3[N:22]=[C:21]([CH3:26])[NH:20][C:19](=[O:27])[C:18]=3[CH2:17]2)=[CH:5][CH:4]=1.[CH2:30]([O:32][C:33](=[O:36])[CH2:34]Br)[CH3:31].C(=O)([O-])[O-].[Cs+].[Cs+]>CN(C=O)C.O>[C:28]([C:16]1([C:6]2[C:7]3[C:11]4[CH:12]=[CH:13][CH:14]=[CH:15][C:10]=4[O:9][C:8]=3[C:3]([O:2][CH3:1])=[CH:4][CH:5]=2)[CH2:25][CH2:24][C:23]2[N:22]=[C:21]([CH3:26])[N:20]=[C:19]([O:27][CH2:34][C:33]([O:32][CH2:30][CH3:31])=[O:36])[C:18]=2[CH2:17]1)#[N:29]To a solution of the compound obtained in example 21 (150 mg, 1.76 mmles) in dry DMF (5 ml) was added ethylbromoacetate (322.3 mg, 1.93 mmol) and cesium carbonate (688 mg, 2.11 mmol). The reaction mass was stirred at room temperature for 1 hr, diluted with water and extracted with ethyl acetate. The organic layer was washed with water followed by brine and dried over sodium sulfate and concentrated under vacuum. The crude product was purified by column chromatography to get both pure compounds.
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