CO[C:3]([C:5]1[CH:6]=[N:7][C:8]2[N:9]([N:21]=[C:22]([CH3:24])[CH:23]=2)[C:10]=1[NH:11][C:12](=[O:20])[CH2:13]C1C=CC=CC=1)=[O:4].C1COCC1.C[Si]([N-][Si](C)(C)C)(C)C.[Na+].C(Cl)Cl>O>[CH3:24][C:22]1[CH:23]=[C:8]2[N:7]=[CH:6][C:5]3[C:3]([OH:4])=[CH:13][C:12]([OH:20])=[N:11][C:10]=3[N:9]2[N:21]=1A 250 mL round bottom flask containing Compound (20-1) (1.62 g, 5.0 mmol, 1 eq.), THF (30 mL), and NaHMDS (7.5 mL, 7.5 mmol, 1.5 eq.) was stirred at room temperature for 2 h. The reaction was treated with CH2Cl2 (30 mL) and water (40 mL). The aqueous phase was extracted with CH2Cl2 (2×15 mL). The water layer was acidified with concentrated HCl (˜10 mL). The precipitated solid was filtered and washed with CH2Cl2 (4 mL) to furnish Compound (20-2) as a yellowish solid. The acidified water layer was extracted with 5% MeOH in CH2Cl2 (3×25 mL). The combined organic phases were dried over Na2SO4. After filtration and concentration, the residue was purified by silica gel chromatography using MeOH and CH2Cl2 as the mobile phases to furnish Compound (20-2) as a yellowish solid.
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