Cl[C:2]([O:4][CH2:5][C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1)=[O:3].[NH2:12][C:13]1[C:14](=[O:22])[NH:15][C:16]([CH2:19][CH2:20][CH3:21])=[CH:17][CH:18]=1>O1CCOCC1.[OH-].[Na+].O.C(=O)([O-])[O-].[Na+].[Na+]>[CH2:5]([O:4][C:2]([NH:12][C:13]1[C:14](=[O:22])[NH:15][C:16]([CH2:19][CH2:20][CH3:21])=[CH:17][CH:18]=1)=[O:3])[C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1Benzyl chloroformate (1.8 ml, 12.6 mmol) was added to a solution of 3-amino-6-propyl-2-pyridinone (1.63 g, 10.8 mmol) in a mixture of dioxane (25 ml) and 1N NaOH at 0° C. Within minutes a white precipitate formed. The reaction mixture was stirred at the same temperature for 1 h then at room temperature for 1 h. The reaction mixture was diluted with water and extracted with ethyl acetate then methylene chloride. Each extract was washed with brine then combined and dried over magnesium sulfate. Removal of the solvents in vacuo gave a yellow semi-solid which was a mixture of starting material and product. This was redissolved in a mixture of dioxane (24 ml) and 10% aqueous sodium carbonate (12 ml) and cooled to 0° C. Benzyl chloroformate (1.5 ml, 10.5 mmol) was once again added and after stirring for 0.5 h, the reaction mixture was allowed to stir at room temperature for 3 h. After dilution with water, the precipitate was filtered off and washed thoroughly, first with water and then with ether. Drying gave the title compound as a white powder: 1H NMR (CDCl3) d 0.96 (t, J=7.3 Hz, 3 H), 1.68 (m, 2 H), 2.52 (t, J=7.5 Hz, 2 H), 5.22 (s, 2 H), 6.07 (d, J=7.5 Hz, 1 H), 7.34-7.43 (m, 4 H), 7.68 (s, 1 H), 8.05 (br d, J=5.3 Hz, 1 H).
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