Abstract
A new series of 4,5-disubstituted-2,4-dihydro-3H-1,2,4-triazole-3-thiones (6a-s) and 2,5-disubstituted-1,3,4-thiadiazoles (7a-h) was synthesized by intramolecular dehydrocyclization of various 1,4-disubstituted thiosemicarbazide derivatives (5a-s) by refluxing in 4N aqueous sodium hydroxide and by overnight stirring with polyphosphoric acid, respectively. The structures of these compounds were characterized by IR, H-1 and C-13 NMR, elemental analysis and mass spectroscopic studies. All the synthesized compounds were screened for their acetylcholinesterase and alkaline phosphatase inhibition studies. Most of the tested compounds showed promising activities, amongst them (6k) and (6q) showed excellent acetylcholinesterase inhibitory activity with IC50 0.241 +/- 0.012 and 0.260 +/- 0.013 mu M, respectively, as compared with those of standard drug whereas the compound (6p), with IC50 0.044 +/- 0.001 mu M, was found to be the most potent inhibitor of alkaline phosphatase.