Synthesis, biological evaluation, and in silico studies of novel chalcone- and pyrazoline-based 1,3,5-triazines as potential anticancer agents

Abstract

A novel series of triazin-chalcones (7,8)a-g and triazin-N-(3,5-dichlorophenyl)pyrazolines (9,10)a-g were synthesized and evaluated for their anticancer activity against nine different cancer strains. Triazine ketones 5 and 6 were synthesized from the cyanuric chloride 1 by using stepwise nucleophilic substitution of the chlorine atom. These ketones were subsequently subjected to a Claisen-Schmidt condensation reaction with aromatic aldehydes affording chalcones (7,8)a-g. Then, N-(3,5-dichlorophenyl)pyrazolines (9,10)a-g were obtained by cyclocondensation reactions of the respective chalcones (7,8)a-g with 3,5-dichlorophenylhydrazine. Among all the evaluated compounds, chalcones 7d,g and 8g exhibited more potent in vitro anticancer activity, with outstanding GI₅₀ values ranging from 0.422 to 14.9 μM and LC₅₀ values ranging from 5.08 μM to >100 μM. In silico studies, for both ligand- and structure-based, were executed to explore the inhibitory nature of chalcones and triazine derivatives. The results suggested that the evaluated compounds could act as modulators of the human thymidylate synthase enzyme.

Fig. 1. Triazine derivatives with different anticancer activity mechanisms.

Scheme 1. Synthetic pathway for triazine derivatives 5 and 6. Reagents and conditions: (i) 4-aminoacetophenone; acetone, −5–0 °C, 5 h; (ii) morpholine, acetone, −5–0 °C, 6 h; (iii) 4-chloroaniline, dioxane, room temperature, 12 h; (iv) ethanolamine, dioxane, reflux, 8h.

Scheme 2. Synthesis of N-(3,5-dichlorophenyl)pyrazolines 9a–g and 10a–g and their precursor chalcones 7a–g and 8a–g. Reagents and conditions: (i) benzaldehyde–R₂, 20% KOH, ethanol, 3–8 h; (ii) 3,5-dichlorophenylhydrazine hydrochloride, ethanol, reflux, 12 h.

Fig. 2. Comparison of the mean GI₅₀ values, per panel, displayed by chalcones 7d,g, 8g and the standard drug 5-fluorouracil (5-FU) against the 60 human cancer cell lines.

Fig. 3. Thymidylate synthase dimer (from PDB ID 5X5Q).

Fig. 4. Amino acid maps representations of the best scored derivatives (7d,g and 8g).

Fig. 5. Left: superposition of 8g (white) and raltitrexed (green). Right: stacking interaction between 8g (green) and UMP (white).