[C:1]([O:5][C:6]([NH:8][CH:9]([C:13]([CH3:16])([CH3:15])[CH3:14])[C:10](O)=[O:11])=[O:7])([CH3:4])([CH3:3])[CH3:2].ClC(OCC(C)C)=O.C[N:26]1CCOCC1.[OH-].[NH4+]>C1COCC1.[Cl-].[Na+].O>[NH2:26][C:10]([CH:9]([NH:8][C:6](=[O:7])[O:5][C:1]([CH3:4])([CH3:3])[CH3:2])[C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11]
A stirred solution of Example 22A (1.81 g, 7.83 mmol) in THF (20 mL) at−40° C. was treated with isobutyl chloroformate (1.01 mL, 7.83 mmol) followed by N-methylmorpholine (0.860 mL, 7.83 mmol). After 15 minutes, the milky white reaction mixture was treated dropwise with ammonium hydroxide (6.0 mL of 30% reagent, 15.0 mmol), the reaction flask was warmed to −15° C., stirred for 45 minutes, treated with brine (20 mL), and the clear homogeneous mixture was extracted with ethyl acetate (2×40 mL). The organic portions were combined, washed with aqueous KHSO4 solution (15 mL), aqueous NaHCO3 solution (15 mL), and brine (15 mL), and dried (MgSO4). Filtration and removal of solvent provided 1.68 g of the desired product as a white solid.
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