C1N2CN3CN(C2)CN1C3.C1CCN2C(=NCCC2)CC1.[CH3:22][O:23][C:24]([CH:26]1[CH2:30][O:29][C:28]([CH2:31][CH:32]([C:39]2[CH:44]=[CH:43][CH:42]=[CH:41][CH:40]=2)[CH2:33][C:34]([O:36][CH2:37][CH3:38])=[O:35])=[N:27]1)=[O:25]>C(Cl)Cl>[CH3:22][O:23][C:24]([C:26]1[N:27]=[C:28]([CH2:31][CH:32]([C:39]2[CH:40]=[CH:41][CH:42]=[CH:43][CH:44]=2)[CH2:33][C:34]([O:36][CH2:37][CH3:38])=[O:35])[O:29][CH:30]=1)=[O:25]To a suspension of CuBr2 (1.17 g, 5.26 mmole) in degassed (3×vacuum/N2) CH2Cl2 (6 mL) was added hexamethylenetetramine (737 mg, 5.26 mmole) then DBU (0.78 mL, 5.26 mmole). After 5 min, a solution of ethyl (±)-4-(4-methoxycarbonyl-1,3-oxazolin-2-yl)-3-phenylbutanoate (420 mg, 1.32 mmole) in CH2Cl2 (2 mL) was added dropwise. After 6 hr, the mixture was filtered through a pad of silica gel (EtOAc) and the filtrate was concentrated under reduced pressure. The residue was chromatographed on silica gel (50% EtOAc/hexanes) to give the title compound (267 mg, 64%) as a white solid: MS (ES) m/e 318 (M+H)+.
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