C[O:2][C:3](=[O:19])[CH:4]([NH:8][C:9]([O:11][CH2:12][C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1)=[O:10])[CH2:5][O:6][CH3:7].C([O-])([O-])=O.[K+].[K+]>CO>[C:9]([NH:8][CH:4]([CH2:5][O:6][CH3:7])[C:3]([OH:19])=[O:2])([O:11][CH2:12][C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1)=[O:10]Compound 10 (0.58 g) was dissolved in 80% aqueous methanol (3.0 mL). To this solution was added anhydrous K2CO3 (0.5 g) and the reaction mixture was stirred at room temperature (8 hours). The methanol was evaporated in vacuo and the residue suspended in water (50 mL). The aqueous suspension was washed with ethyl ether (2×25 mL) and then acidified to pH 3.0 using 5N HCl. The acidified aqueous phase was extracted with ethyl acetate (3×25 mL). The ethyl acetate extracts were combined, dried (Na2SO4), filtered, and evaporated in vacuo to obtain pure 11 as a clear viscous oil (0.52 g, 95%): Rf 0.30 (10% MeOH/CHCl3).
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