Synthesis and Evaluation of Antifungal and Antitrypanosomastid Activities of Symmetrical 1,4-Disubstituted-1,2,3-Bistriazoles Obtained by CuAAC Conditions
Authors: Victor Mauricio M. , Farias Ravir R. , da Silva Danielle L. , do Carmo Paulo H.F. , de Resende-Stoianoff Maria A. , Viegas Cláudio , Espuri Patrícia F. , Marques Marcos J. 
Published: October 2018

Background:
The trypanosomatids, such as the protozoan Leishmania spp., have a demand
by ergosterol, which is not present in the membrane from mammal cells. The suppression of
the synthesis of ergosterol would be a new target of compounds with leishmanicidal activity, and
bistriazole has shown trypanocidal activity by this mechanism. The incidence of fungal infections
has increased at an alarming rate over the last decades. This is related both to the growing population
of immune-compromised individuals and to the emergence of strains that are resistant to
available antifungals. Therefore, there is a challenge for the search of potential new antifungal
agents.

Objective:
The study aimed to synthesize 1,4-disubstituted-1,2,3-bistriazoles by optimized copper(
I)-catalyzed alkyne-azide cycloaddition (CuAAC) and evaluate their antifungal and
antitrypanosomastid activities.

Method:
The synthesis of symmetrical bistriazoles with diazides as spacers was planned to be performed
following the CuAAC reaction strategy. For evaluation of best conditions for the synthesis
of symmetrical bistriazoles hex-1-yne 2 was chosen as leading compound, and a variety of catalysts
were employed, choosing (3:1) alkyne:diazide stoichiometric relationship employing
CuSO4.5H2O as the best condition. For the preparation of diversity in the synthesis of symmetrical
bistriazoles, a 1,3-diazide-propan-2-ol 1a and 1,3-diazidepropane 1b were reacted with seven different
alkynes, furnishing eleven symmetrical bistriazoles 9-13a,b and 14a. All compounds were
essayed to cultures of promastigotes of L. amazonensis (1 x 106 cells mL-1) in the range of 0.10 -
40.00 µg mL-1 and incubated at 25ºC. After 72 h of incubation, the surviving parasites were
counted. For antifungal assay, the minimum inhibitory concentrations (MIC) for yeasts and filamentous
fungi were determined. Each compound was tested in 10 serial final concentrations (64 to
0.125 µg mL-1).

Results:
Eleven 1,4-disubstituted-1,2,3-bistriazoles were synthesized and their structures were
confirmed by IR, 1H and 13C-NMR and Mass spectral analysis. The antifungal and
antitrypanosomastid activities were evaluated. The best result to antifungal activity was reached by
bistriazole 11a that showed the same MIC of fluconazole (32 µg mL-1) against Candida krusei
ATCC 6258, an emerging and potentially multidrug-resistant fungal pathogen. Due to their intrinsically
biological activity versatility, five derivatives compounds showed leishmanicidal inhibitory
activity between 15.0 and 20.0% at concentrations of 20 and 40.0 µg mL-1. Among these
compounds the derivative 13a showed best IC50 value of 63.34 µg mL-1 (182.86 µM).

Conclusion:
The preliminary and promising results suggest that bistriazole derivatives, especially
compound 13a, could represent an innovative scaffold for further studies and development of new
antifungal and anti-parasitic drug candidates.