Heat shock proteins are molecular chaperons that are essential for maintaining the native conformation of other proteins both under physiological conditions and in a stressful environment. In the latter, their role is even more important because their expression is increased and, at the same time, a greater number of client proteins are misfolded and dependent on the action of heat shock proteins. Of particular importance in cancer pathophysiology, is the Hsp90 protein that is critical for maintaining the proper conformation, stability and function of many oncoproteins that are important for maintaining the malignant properties of cancer cells. Hsp90 inhibitors therefore represent both potential and already validated antitumour agents. Due to the induction of heat shock and the resulting side effects of inhibitors targeting N-terminal domain of Hsp90, the researches have mainly focused on the synthesis of C-terminal inhibitors.
In this Master’s thesis, we synthesised 5 potential inhibitors of the C-terminal domain of Hsp90 with a triazole core structure. All inhibitors are substituted with a phenyl(piperazin-1-yl)methanone group at position 1 of the triazole ring, while the synthesised compounds differ in the substituents at position 4 of the central triazole ring. The final compounds were prepared in four steps. First, azide and alkyne were synthesised and combined in a click reaction. Different synthetic procedures were used for the preparation of azides and alkynes such as amide bond synthesis with coupling reagents, Williams synthesis of ethers and amide bond synthesis by activation of the carboxylic acid to the acid chloride. In the final step, the tert-butyl protecting group was removed from the compound to give the final products.
The final compounds were screened for their inhibitory activity on the MCF-7 breast cancer cell line using the MTS assay and compared with compound TJD-52, on which our design was based. Synthesised compounds 6a, 10a and 10c have stronger inhibitory activity than the reference compound TJD-52. Compound 6a (IC50 (MCF-7) = 3.5 ± 0.9 µM), which has an N-methylindole ring linked to position 4 of the triazole scaffold via an amide bond, was found to be the most effective compound. It also contains a larger lipophilic moiety that forms several hydrophobic interactions, which may also contribute positively to the activity. In addition, we found that the distance between the lipophilic moiety and the triazole is important and was most optimal for the reference compound TJD-52. Moreover, the ether linker increases the flexibility of the molecule, leading to a different fit to the binding site and, in the case of our compound, to a weaker activity. The results make an important contribution to the understanding of the structure-activity relationship of triazole inhibitors of Hsp90, which would be worth further investigation in the future.
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