[CH2:1]([C:3]1[NH:4][C:5](=[O:15])[C:6](=[CH:9][C:10]=1[C:11](=[O:14])[CH2:12][CH3:13])[C:7]#N)[CH3:2].[OH2:16].S(=O)(=O)(O)[OH:18]>C(O)(=O)C>[CH2:1]([C:3]1[NH:4][C:5](=[O:15])[C:6](=[CH:9][C:10]=1[C:11](=[O:14])[CH2:12][CH3:13])[C:7]([OH:18])=[O:16])[CH3:2]A mixture containing 40.8 g of 6-ethyl-1,2-dihydro-2-oxo-5-(n-propanoyl)nicotinonitrile, 50 ml of water, 75 ml of concentrated sulfuric acid and 200 ml of acetic acid was heated on a steam bath for 8 hours, cooled and concentrated on a rotary evaporator to remove the acetic acid and water. The remaining mixture was diluted with 300 ml of water and chilled for 1 hour in an ice bath. The white solid that separated was collected, washed with water and dried in a vacuum over at 80° C. and recrystallized from isopropyl alcohol-ether and dried in a vacuum oven at 90° C. to yield 34.6 g of 6-ethyl-1,2-dihydro-2-oxo-5-(n-propanoyl)nicotinic acid, m.p. 180°-182° C.
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