[NH2:1][C:2]1[C:3]([NH:12][CH2:13][C:14]2[CH:19]=[CH:18][C:17]([C:20]3[CH:25]=[CH:24][CH:23]=[CH:22][C:21]=3[C:26](=[NH:34])[NH:27][O:28][C:29]([O:31][CH2:32][CH3:33])=[O:30])=[CH:16][CH:15]=2)=[C:4]([CH:9]=[CH:10][CH:11]=1)[C:5]([O:7][CH3:8])=[O:6].[CH2:35]([O:37][C:38](OCC)(OCC)OCC)[CH3:36].C(O)(=O)C>O1CCOCC1>[CH2:35]([O:37][C:38]1[N:12]([CH2:13][C:14]2[CH:19]=[CH:18][C:17]([C:20]3[CH:25]=[CH:24][CH:23]=[CH:22][C:21]=3[C:26](=[NH:34])[NH:27][O:28][C:29]([O:31][CH2:32][CH3:33])=[O:30])=[CH:16][CH:15]=2)[C:3]2[C:4]([C:5]([O:7][CH3:8])=[O:6])=[CH:9][CH:10]=[CH:11][C:2]=2[N:1]=1)[CH3:36]The pale brown syrup (8.58 g) obtained in Example (57a) was dissolved in dioxane (20 ml). To the solution were added tetraethoxymethane (8.64 g) and acetic acid (1.56 g). The mixture was stirred for 2 hours at 100° C. The reaction mixture was concentrated to dryness. The residue was crystallized from ethyl acetate (50 ml). Resulting crystalline precipitates were collected by filtration to obtain the title compound.
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