[C:1]([O:5][C:6]([NH:8][C@@H:9]([C:13]([O:16][CH3:17])([CH3:15])[CH3:14])[C:10]([OH:12])=[O:11])=[O:7])(C)(C)C.FC(F)(F)C(O)=O.[OH-].[Na+].ClC(OC)=O>C(Cl)Cl.CCOC(C)=O>[CH3:17][O:16][C:13]([CH3:15])([CH3:14])[C@H:9]([NH:8][C:6]([O:5][CH3:1])=[O:7])[C:10]([OH:12])=[O:11]To a solution of Example 203B (163 mg, 0.66 mmol) in CH2Cl2 (2 mL) was added trifluoroacetic acid (2 mL) and the solution was stirred at room temperature for 1 h. Solvent was removed in vacuo and the residue was suspended in saturated NaHCO3, extracted with EtOAc, the organic extracts combined, washed with brine, dried (Na2SO4), filtered and solvent removed in vacuo. The residue was dissolved in dioxane (1 mL) and 1 M NaOH (1.1 mL, 2.175 mmol) was added followed by the dropwise addition of methyl chloroformate (0.102 mL, 1.3 mmol). The solution was stirred at room temperature for 16 h, diluted with EtOAc, washed with 1 N HCl, brine, dried (Na2SO4), filtered and solvent removed in vacuo to give the title compound (96 mg, 0.468 mmol, 71%).
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