[C:1]([CH:8]1[CH2:13][C:12]2([CH2:16][NH2:17])[CH2:14][CH2:15][C:9]1([C:18]([OH:20])=O)[CH2:10][CH2:11]2)([O:3][C:4]([CH3:7])([CH3:6])[CH3:5])=[O:2].C(N1C=CN=C1)([N:23]1C=CN=C1)=O.[NH4+].[OH-].O>CN(C=O)C>[C:1]([CH:8]1[CH2:13][C:12]2([CH2:16][NH2:17])[CH2:11][CH2:10][C:9]1([C:18]([NH2:23])=[O:20])[CH2:15][CH2:14]2)([O:3][C:4]([CH3:7])([CH3:6])[CH3:5])=[O:2]A stirred solution under N2 of 12.0 g (42.5 mmol) of the product from step B in 100 ml of DMF was treated with 8.0 g (49.3 mmol) of carbonyldiimidazole. After 30 min the DMF was evaporated in vacuo to afford 50-60 ml of a light brown paste, which was stirred and treated with 70 ml of conc. NH4OH rapidly added. The initial solution turned to a white paste within 30 min, after which H2O was added up to a total volume of 400 ml to complete precipitation of product, which was triturated and isolated by filtration and washing with H2O, and dried in vacuo to yield the title compound as a white solid.
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