Studies on anticoccidial agents. 11. Synthesis and anticoccidial activity of nitropyridinecarboxamides and derivatives

Of the nine nitropyridinecarboxamides, which are isomers of 5-nitronicotinamide, a potent anticoccidial agent, 2-nitropyridine-3, -4, -5-, or 6-carboxamides and 3-nitropyridine-4- or 6-carboxamides were prepared from the corresponding acids via the esters of the acid chlorides. 3-Nitropyridine-2-carboxamide was obtained from 2-methyl-3-nitropyridine by oxidation with SeO2, oximation, dehydration with Ac2O, and hydrolysis with H2SO4. 4-Nitropyridine-2-carboxamide was prepared from 2-cyano-4-nitropyridine by hydrolysis, and the 3-carboxamide analogue was obtained from 4-amino-3-cyanopyridine by oxidation with H2O2 and fuming H2SO4. Of these compounds 2-nitro- and 3-nitro- but not 4-nitropyridinecarboxamides were found to be active against Eimeria tenella. N-Substituted analogues of 2-nitro- and 3-nitropyridine carboxamides were also prepared in a conventional manner and optimal anticoccidial activity was attained with 2-nitroisonicotinamide and its N-alkanoyl, N-aromatic, and N-heterocyclic acyl derivatives.

Studies on anticoccidial agents. 10. Synthesis and anticoccidial activity of 5-nitronicotinamide and its analogues

5-Nitronicotinamide (1) was prepared from 5-bromonicotinoyl chloride by treatment with ammonia and then oxidation with fuming H2SO4 and 30% H202. 2-Cholor-, 2-alkoxy-2-benzyloxy,2-phenoxy-,2-alkylamino-, and 2-benzylamino-5-nitronicatinamides were also prepared via 2-chloro-3-cyano-5-nitropyridine. 2-Methyl-5-nitronicotinamide (2) was obtained from ethyl 2-methyl-5-nitronicotinate by treatment with ammonia; the 4-methyl analogue 3 was from 3-cyano-2,6-dihydroxy-4 methylpyridine by nitration, chlorination, and dechlorination, and the 6-methyl analogue 4 was prepared by transforming 2-chloro-3-cyano-6-methyl-5-nitropyridine to the corresponding amide, followed by dechlorination. Of these compounds, the 5-nitronicotinamide, the 2-methyl and 4-methyl but not the 6-methyl, analogue showed significant anticoccidial activity against eimeria tenella. N-Substituted analogues of 5-nitronicotinamide and 2-methyl-5-nitronicotinamide were prepared in a conventional manner and optimal anticoccidial activity was attained with their lower N-alkyl analogues, N-alkanoyl and -alkenoyl analogues, and N-aromatic acyl analogues together with these parent compounds.

Determination of micro amounts of 3-(dithien-2-ylmethylene)-1-methylpiperidine, a non-narcotic antitussive

A specific colorimetric method for the determination of micro amounts of 3-(dithien-2-ylmethylene)-1-methylpiperidine, a new antitussive and expectorant, is described. Depending on amount, a characteristic colour varying from rose pink to deep bluish purple appears when 2 volumes of a 0·01% solution of ninhydrin in concentrated sulphuric acid are added to 1 volume of an aqueous solution of the drug. After 24 hr at room temperature the colour produced has an absorption maximum at 590 mμ and follows Beer's Law over the range 1–25 μg/ml. The colour is specific for the drug and is sensitive at the μg/ml level. Recoveries from aqueous solution and human urine were 97·4 ± 2·1 and 97·4 ± 1·7% respectively.