[O-]CC.[Na+].CO[C:7]([C:9]1[CH2:10][O:11][CH2:12][C:13]=1[N:14]([CH2:23][C:24]1[CH:29]=[CH:28][C:27]([Br:30])=[CH:26][CH:25]=1)[C:15](=[O:22])[CH2:16][C:17]([O:19][CH2:20][CH3:21])=[O:18])=[O:8].CCOC(C)=O>C(O)C.ClCCl>[Br:30][C:27]1[CH:26]=[CH:25][C:24]([CH2:23][N:14]2[C:15](=[O:22])[C:16]([C:17]([O:19][CH2:20][CH3:21])=[O:18])=[C:7]([OH:8])[C:9]3[CH2:10][O:11][CH2:12][C:13]2=3)=[CH:29][CH:28]=1A solution of sodium ethoxide (0.671 g, 9.85 mmol) in ethanol (50 ml) was added to the N-acylated enamine from Step B (2.8 g, 6.57 mmol). This reaction mixture was heated in a sealed vial at 85° C. for 4 h. The reaction mixture was concentrated in vacuo to give a maroon oil. To this oil was added sat. NaH2PO4 (50 mL) and EtOAc (50 mL) and the layers were separated. The aqueous layer was then extracted with EtOAc (3×40 mL). The combined organic extracts were washed with water (40 mL), brine (40 mL), dried over MgSO4, and concentrated in vacuo to give a yellow oil. The oil was taken up in dichloromethane, Et2O and hexanes and concentrated several times until a solid formed. The solid was triturated with Et2O and filtered to give compound 28-3 as a tan solid, 563 mg: 1H NMR (500 MHz, CDCl3): δ 1.45 (t, 3 H, J=7.1 Hz), 4.46 (q, 2 H, J=7.1 Hz), 4.89 (t, 2 H, J=3.0 Hz), 4.98 (s, 2 H), 5.03 (t, 2 H, J=3.2 Hz), 7.10 (d, 2 H, J=8.5 Hz), 7.45 (d, 2 H, J=8.5 Hz); HPLC/MS: 1.17 min, 395.0 (M+H)+.
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