Synthesis of triazole bridged N-glycosides of pyrazolo[1,5- a]pyrimidinones as anticancer agents and their in silico docking studies

Abstract

In the pursuit of novel therapeutic agents, we present a comprehensive study on the design, synthesis, and evaluation of a diverse library of triazole bridged N-glycosides of pyrazolo[1,5-a]pyrimidinones, employing a microwave-assisted synthetic approach via 'click chemistry'. This methodology offers efficient and accelerated access to the glycohybrids, showcasing improved reaction conditions that yield high-quality products. In this research endeavor, we have successfully synthesized a series of twenty-seven triazole bridged N-glycosides of pyrazolo[1,5-a]pyrimidinones. Our investigation extends beyond synthetic endeavors to explore the potential therapeutic relevance of these compounds. We subjected them to rigorous in vitro screening against prominent breast cancer cell lines MCF-7, MDA-MB231, and MDA-MB453. Among the library of compounds synthesized, (2S,3S,4R,5S,6S)-2-(acetoxymethyl)-6-(4-((5-(4-methoxyphenyl)-7-oxopyrazolo[1,5-a]pyrimidin-1(7H)-yl)methyl)-1H-1,2,3-triazol-1-yl)tetrahydro-2H-pyran-3,4,5-triyl triacetate emerged as a potent compound, exhibiting remarkable anti-cancer activity with an IC₅₀ value of 27.66 μM against the MDA-MB231 cell line. Additionally, (2S,3R,4R,5S,6S)-2-(acetoxymethyl)-6-(4-((7-oxo-5-(4-(trifluoromethyl)phenyl)pyrazolo[1,5-a]pyrimidin-1(7H)-yl)methyl)-1H-1,2,3-triazol-1-yl)tetrahydro-2H-pyran-3,4,5-triyl triacetate displayed notable inhibitory potential against the MCF-7 cell line, with an IC₅₀ value of 4.93 μM. Furthermore, in silico docking analysis was performed to validate our experimental findings. These findings underscore the promise of our triazole bridged N-glycosides of pyrazolo[1,5-a]pyrimidinones as potential anti-cancer agents. This research not only enriches the field of glycohybrid synthesis but also contributes valuable insights into the development of novel anti-cancer therapeutics.

Fig. 1. Pyrazolo-pyrimidine based privileged scaffolds (A–F): (A) formycin, antibacterial, (B) Sildenafil, treatment of erectile dysfunction (C) oxoformycin, antibacterial drug (D) Zaleplon, anti-Insomnia drug, (E) Cox-2 inhibitor, anti-inflammatory agent, (F) our designed molecule.

Scheme 1. Synthesis of N-propargylated pyrazolo[1,5-a]pyrimidinones 10–18. In all cases, O-propargylated products were also formed as a minor product but the yields reported here are for N-propargylated products.

Scheme 2. Synthesis of triazole bridged N-glucosides 22–30.

Scheme 3. Synthesis of triazole bridged N-galactosides 31–39.

Scheme 4. Synthesis of triazole bridged N-mannosides 40–48.

Fig. 2. Anti-cancer activity at different dilutions for active compounds were found at 10 μM, 25 μM, and 50 μM for compound 23, 26, 30, 33, 36 and 41 respectively compared to DMSO (control).

Fig. 3. IC₅₀ of the most active compounds. To calculate half maximal inhibitory concentration (IC₅₀) of compounds 23, 26, 30, 33, 36 and 41 MDA-MB-231 cells were treated for 72 h with different concentrations (10, 25 and 50 μM) of the respective drugs and tested for cell viability by the MTT assay. IC₅₀ values were determined by plotting values of percent cell viability against concentration of each of these compounds. IC₅₀ values for compounds 23, 26, 30, 33, 36 and 41 against MDA-MB-231 breast cancer cell line were found 27.66, 54.85, 39.48, 45.98, 32.12, and 37.57 μM, respectively. The experiments were performed in triplicates, n = 3 and ± SD value was calculated for each data point.

Fig. 4. IC₅₀ of the most active compounds. To calculate half maximal inhibitory concentration (IC₅₀) of compounds 23, 26, 30, 33, 36 and 41 MCF-7 cells were treated for 72 h with different concentrations (10, 25 and 50 μM) of the respective drugs and tested for cell viability by the MTT assay. IC₅₀ values were determined by plotting values of percent cell viability against concentration of each of these compounds. The IC₅₀ values for compound 23, 26, 30, 33, 36 and 41 against MCF-7 breast cancer cells line were found 9.24, 26.64, 18.49, 7.32, 4.93, 21.76 μM, respectively. The experiments were performed in triplicates, n = 3 and ± SD value was calculated for each data point.

Fig. 5. Docking analysis of triazole-bridged N-glycosides of pyrazolo[1,5-a]pyrimidinones (compounds 23, 26, 30, 33, 36 and 41) and catalytic site of ER-α protein with 3D representation of hydrogen bond donor/acceptor surface (shown in pink and green colour) and hydrogen bond (green color). The docking analysis was conducted using the collected set of compounds (gray) into the proposed binding pocket of the X-ray crystallographic structure of ER-α protein (Protein Data Bank ID: 1A52, resolution: 2.6 Å).

Fig. 6. 2D representation of docked results of compound 36.