C[O:2][C:3](=[O:23])[CH2:4][C:5]1([CH2:21][CH3:22])[C:10]2[NH:11][C:12]3[C:17]([C:9]=2[C:8](=[O:20])[CH2:7][O:6]1)=[CH:16][CH:15]=[CH:14][C:13]=3[CH2:18][CH3:19]>CO.O>[CH2:21]([C:5]1([CH2:4][C:3]([OH:23])=[O:2])[C:10]2[NH:11][C:12]3[C:17]([C:9]=2[C:8](=[O:20])[CH2:7][O:6]1)=[CH:16][CH:15]=[CH:14][C:13]=3[CH2:18][CH3:19])[CH3:22]A solution of the product produced in step B (1.25 g, 3.9 mmol), K2 CO3 (3.5 g, 25.3 mmol) and 60 ml MeOH/H2O 1:1 was refluxed for 3 h. The methanol was evaporated, and the aqueous residue acidified to pH 1 using 6N HCl. The aqueous phase was extracted with EtOAc. The organic phase was washed with water, dried (MgSO4), and evaporated to produce a crude glass which was recrystallized from EtOAc-hexane to afford 1.1 g of the title compound as a solid, m. p. 198°-201° C.
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