C(O[C:4](=[O:15])[CH:5]([CH3:14])[C:6](=[O:13])[CH2:7][C:8]([O:10][CH2:11][CH3:12])=[O:9])C.C(OC(O[CH2:22][CH3:23])=C)C.[CH3:24][NH2:25]>C(OCC)C.C[O-].[Na+]>[CH2:11]([O:10][C:8]([C:7]1[C:6]([OH:13])=[C:5]([CH3:14])[C:4](=[O:15])[N:25]([CH3:24])[C:22]=1[CH3:23])=[O:9])[CH3:12]A mixture of 2-methyl-3-oxo-pentanedioic acid diethyl ester (10.0 g, 46.3 mmol), 1,1-diethoxy-ethene (12.8 mL, 92.5 mmol) and sodium methoxide (0.026 mg, 0.481 mmol) was heated to 85° C. for nine hours. The reaction mixture was cooled to room temperature and concentrated. To the resulting residue was added methylamine (1.91 mL, 55.5 mmol, 40% H2O). After stirring at room temperature for 16 hours, the reaction mixture was diluted with diethyl ether and washed with water. The aqueous phase was acidified to pH 1 with 10% HCl solution and extracted with EtOAc. The organic layer was dried (MgSO4) and concentrated. Trituration of the resulting residue with diethyl ether and flash column chromatography (3% MeOH in methylene chloride) gave 3.55 g (34%) desired product.
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