Design, Synthesis, And Anti-trypanosomal Activities Of Small Molecule Inhibitors Of Cystein Protease Of Trypanosoma Cruzi

In this thesis, we tried to do basic research on developing new antitrypanosomal agents targeted the cysteine protease of Tryponosoma Cruzi (cruzain). Total 239 compounds out of seven series lead structures were designed and synthesized by combining molecular modeling with chemical modification, 234 of which are new compounds that had never been reported. The structures of synthesized compounds were confirmed by 'H-NMR spectroscopy, IR. and HRMS(EI). The bioassay of the compounds against cruzain in vitro, and the cell culture assay against T. cruzi have been done. The activity-structures relationship (SAR) of these compounds and the inhibition mechanism of thiosemicarbazone scaffolds have also been explored.Aroyl thiourea and bis-substituted urea scaffolds were identified through a computational screen of the ACD database with program DOCK. Basing on those results and associating with the pharmaceutical theory for drug design, we chose six-five combination aryl heterocylic ring and benzyloxy aniline or benzylamino aniline as the synthetic blocks. Total 23 compounds of Aroyl thiourea scaffold. 95 compounds of bis-substituted urea scaffold, 25 compounds of thiourea scaffold were designed and prepared. The assay of these compounds against cruzain in vitro have been done, and inhibitor tf-175 was selected to be the control drug. The results showed that: all aroyl thioureas exhibited certain activities against crizain in vitro, 5 of this series compounds have the IC50 values below 1M, 1 compound exhibited better activity than tf-175; 32 of bis-substituted ureas have the IC50 values below 1M, 10 of which exhibited better activity than tf-175; all bis-substituted thioureas exhibited poor activities against cruzain in vitro, all of their IC50 values are more than 1M. 8 compounds of these three series scaffolds were selected to test the cell culture assay against T. cruzi. Typically, infected host cells die within 5 days without treatment. In contrast, infected host cells treated with A15 (at 10 M) survived 8 days, treated with B59 (10 M) survived 6 days, treated with B65 (at 10M) survived 7 days, others are as same as the block control. The compound B52 are toxicity to host cells in the cell culture assay.As part of a collaborative effort with Parke-Davis, a library of Parke-Davis compounds was screened. Then thiosemicarbazone scaffold and semicarbazone scaffold were identified as activeagainst cruzain. Basing the structural characteristics of thiosemicarbazone and semicarbazone, we designed the pyrazoline and pyrazole analogs in order to find more active, trypanocidal analogs. Total 52 compounds of thiosemicarbazone, 11 compounds of semicarbazone, 26 compounds of pyrazoline, and 7 compounds of pyrazole were designed and prepared. The assay of these compounds against cruzain in vitro have also been done, the thiosemicarbazone and pyrazoline scaffolds exhibited activities against crizain in vitro. In the cell culture assay against T. Cruzi, 12 compounds have been found to survive the infected host cells more than 46 days. No parasites were observed in supernatants or host cells after removing the inhibitors at day 46.