[CH2:1]([O:3][C:4]([C:6]1[C:7]([CH3:21])=[N:8][C:9]([NH2:20])=[C:10]([N+:17]([O-])=O)[C:11]=1[NH:12][CH2:13][CH2:14][CH2:15][CH3:16])=[O:5])[CH3:2]>[Zn].C(O)(=O)C>[NH2:17][C:10]1[C:11]([NH:12][CH2:13][CH2:14][CH2:15][CH3:16])=[C:6]([C:4]([O:3][CH2:1][CH3:2])=[O:5])[C:7]([CH3:21])=[N:8][C:9]=1[NH2:20]29.6 g. of 6-amino-4-butylamino-2-methyl-5-nitropyridine-3-carboxylic acid ethyl ester are dissolved in 150 ml. of acetic acid. The solution is heated at reflux temperature. Zinc is added carefully until the mixture is colorless (about 20 g.). Heating is continued for an additional 10 minutes. The mixture is then evaporated to dryness and about 100 ml. of water are added. The solution is then neutralized with aqueous ammonia and extracted three times with 100 ml. portions of ether. The ether extracts are combined, dried with calcium chloride and the solvent is evaporated. The oily residue of 5,6-diamino-4-butylamino-2-methylnicotinic acid, ethyl ester crystallizes from methanol, yield: 21 g. (79%), m.p. 82°-83° (methanol/H2O).
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