Br[C:2]1[C:10]2[O:9][C:8]([C:11]3[CH:16]=[CH:15][C:14]([OH:17])=[CH:13][CH:12]=3)=[CH:7][C:6]=2[CH:5]=[C:4]([OH:18])[CH:3]=1.C[O-].[Na+].Cl.C[CH2:24][O:25]C(C)=O>CN(C=O)C>[OH:17][C:14]1[CH:15]=[CH:16][C:11]([C:8]2[O:9][C:10]3[C:2]([O:25][CH3:24])=[CH:3][C:4]([OH:18])=[CH:5][C:6]=3[CH:7]=2)=[CH:12][CH:13]=1A solution consisting of 58 (1.5 g, 4.9 mmol) in DMF (25 mL) was treated with CulBr (1.0 g, 6.5 mmol) and NaOMe (6 mL, 4.4 N in MeOH, 27 mmol) and heated to 160° C. for approximately 1 hour. The reaction mixture was allowed to cool and then worked up by adding 2 N HCl and EtOAc. The EtOAc layer was washed with NaHCO3 aq, brine and dried over MgSO4. The solution was concentrated and chromatographed on silica gel (1:4 EtOAc/hexanes to 3:7 EtOAc/hexanes) to yield 0.47 g of pdt: Mp=167–168° C., 1H NMR (DMSO-d6) δ 9.84 (br s, 1 H), 9.18 (br s, 1 H), 7.67 (d, 2 H, J=8.6 Hz), 6.99 (s, 1 H), 6.86 (d, 2 H, J=8.7 Hz), 6.46 (d, 1 H, J=2.1 Hz), 6.34 (d, 1 H, J=2.1 Hz), 3,89 (s, 3 H); MS 257 (M+H)+.
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