The synthesis of 7 contaminants of prothionamide 4a formed during the preparation of prothionamide bulk drug, is described. The products are 2,6–dipropylpyridine-4-carbothioamide 4b, 3-propylpyridine-4-carbothioamide 4c, 2- ethylpyridine-4-carbothioamide 4d, 2-propylisonicotinamide 6, pyridine-4-carbothioamide 4e, 2- propylisonicotinicacid 5, prothionamide sulfoxide 7. Unknown Compounds of 4c and 5-7 were isolated and characterized for the first time. The side products formed during the synthesis of prothionamide intermediate 2- propyl-4-cyanopyridine 3a were also synthesized and characterized as 2,6-dipropyl-4-cyanopyridine 3b, 3-propyl-4- cyanopyridine 3c, 2-ethyl-4-cyanopyridine 3d. The structures of all these compounds were established on the basis of spectral data (IR, 1H-NMR and MS).