[I:1]N1C(=O)CCC1=O.[CH2:9]([O:11][C:12]([C:14]1[CH:19]=[CH:18][C:17](=[O:20])[NH:16][C:15]=1[CH3:21])=[O:13])[CH3:10].O>C(#N)C>[CH2:9]([O:11][C:12]([C:14]1[CH:19]=[C:18]([I:1])[C:17](=[O:20])[NH:16][C:15]=1[CH3:21])=[O:13])[CH3:10]N-Iodosuccinimide (40 g, 180 mmol) was added to a suspension of intermediate (5b), 2-methyl-6-oxo-1,6-dihydro-pyridine-3-carboxylic acid ethyl ester (18.1 g, 100 mmol) in acetonitrile (400 mL), under a nitrogen atmosphere. The resulting suspension was heated at 95° C. for 5 hours to give an initial orange solution. An off-white precipitate slowly formed. The resulting suspension was allowed to cool and was poured into water (1200 mL) to give an off-white precipitate. The separated by filtration and the solids washed with water (500 mL) to give an off-white powder. The solids were dried in vacuo (60° C.) to give the product as an off-white powder, 28.3 g (92%)
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