[OH:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[C:8](=[O:12])[C:7]([C:13]([CH3:17])([CH3:16])[CH:14]=[O:15])=[CH:6][C:5]2=[O:18].I[CH2:20][CH2:21][CH2:22][CH3:23]>CC#N.[Ag]>[CH2:20]([O:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[C:8](=[O:12])[C:7]([C:13]([CH3:16])([CH3:17])[CH:14]=[O:15])=[CH:6][C:5]2=[O:18])[CH2:21][CH2:22][CH3:23]A mixture of 2-(6-Hydroxy-1,4-dioxo-1,4-dihydro-2-naphthalenyl)-2-methylpropanal (compound 3 prepared in step II above) (125 mg, 0.52 mmol) and freshly prepared Ag2O (240 mg, 1.04 mmol) in CH3CN was ultrasonicated for 2 min to disperse the silver salt. Iodobutane (120 μL, 1.05 mmol) was added and the mixture was stirred over night at room temperature. The mixture was filtered on Celite and was washed with EtOAc. The crude product was purified on silica gel with hexane:EtOAc 4:1 but failed to yield pure material. The product was further purified on RP-HPLC. Yield: 53 mg (34%). 1H NMR (400 MHz, CDCl3) δ 0.99 (tr., 3H), 1.40 (s, 6 H), 1.52 (sext., 2 H), 1.82 (quint., 2 H), 4.11 (tr., 2H), 6.87 (s, 1 H), 7.18 (dd, 1 H), 7.48 (d, 1 H), 8.00 (dd, 1 H), 9.72 (s, 1 H).
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