Discovery of Di(het)arylmethane and Dibenzoxanthene Derivatives as Potential Anticancer Agents

Abstract

A family of bifunctional dihetarylmethanes and dibenzoxanthenes is assembled via a reaction of acetals containing a 2-chloroacetamide moiety with phenols and related oxygen-containing heterocycles. These compounds demonstrated selective antitumor activity associated with the induction of cell apoptosis and inhibition of the process of glycolysis. In particular, bis(heteroaryl)methane containing two 4-hydroxy-6-methyl-2H-pyran-2-one moieties combine excellent in vitro antitumor efficacy with an IC₅₀ of 1.7 µM in HuTu-80 human duodenal adenocarcinoma models with a high selectivity index of 73. Overall, this work highlights the therapeutic potential of dimeric compounds assembled from functionalized acetals and builds a starting point for the development of a new family of anticancer agents.

Keywords: anticancer agents; cytotoxic activity; di(het)arylmethane; dibenzoxanthene.

Figure 1

(A) Compounds with anticancer activity containing phenolic moieties. (B) Strategy for the synthesis of new dimeric compounds with anticancer activity [20,21].

Scheme 1

Synthetic route to di(het)arylmethane and dibenzoxanthene derivatives from bifunctional chloro acetal precursors 1a–c. Cyclic substituents introduced by using the acetal moiety are shown in purple and the cationic residues introduced by the reaction of terminal carbonyl chloride are highlighted in red. Reagents and conditions: (a) ClCH₂C(O)Cl, Et₃N, CH₂Cl₂, –5–10 °C, 2 h, 62–95%; (b) CF₃COOH, CHCl₃, rt, 50 h, 20–76%; (c) EtOH, Δ, 72 h, 67–87%; (d) EtOH, Δ, 32 h, 49–79%.

Figure 2

Molecular structure of investigated compound 6b. Ellipsoids are given with a 50% probability.

Scheme 2

Selective activation of α-chloroacetamide moiety followed by double alkylation with the acetal group for the preparation of benzimidazole hybrids 10a,b, 11a–c, 12a–c. Reagents and conditions: (a) benzene-1,2-diamine, DMF, Et₃N, S₈, 40–50 °C, 10 h, 45–63%; (b) CF₃COOH, CHCl₃, rt, 96 h, 38–75%.

Figure 3

The influence of spacer length on activity by the example of compounds 3a,c,e, 4a–c.

Figure 4

The effect of substituents in α-position on the activity of compounds 3c, 4b, 6a,b, 7b, 8, 9b.

Figure 5

The effect of hetarylic substituents on the activity of compounds 3c,d, 4b, 5a,b.

Figure 6

(A)—Induction of apoptosis in HuTu 80 cells incubated with lead compounds. 1. 5a at concentration IC₅₀/2 (1.5 µM); 2. 5a at concentration IC₅₀ (3 µM); 3. 6a at concentration IC₅₀/2 (1 µM); 4. 6a at concentration IC₅₀ (2 µM). L—living cells; D—dead cells; Ea.—early apoptotic cells; La.—late apoptotic cells. (B)—Representative histograms for the number of cells (% of total) in the early and late stages of apoptosis for the control and treatment groups. The values are presented as the mean ± SD; ****—p < 0.0001 versus control. The statistical analysis was performed using two-way ANOVA and the Bonferroni test.

Figure 7

(A)—Effect of lead compounds on the mitochondrial membrane potential in HuTu 80 cells. 1. 5a at concentration IC₅₀/2 (1.5 µM); 2. 5a at concentration IC₅₀ (3 µM); 3. 6a at concentration IC₅₀/2 (1 µM); 4. 6a at concentration IC₅₀ (2 µM). (B)—Quantitative determination of portion of HuTu 80 cells (%) with red and green aggregates. Data are presented as ± SD (n = 3).

Figure 8

Induction of ROS production by lead compounds. 5a at concentration IC₅₀/2 (1.5 µM) and IC₅₀ (3 µM); 6a at concentration IC₅₀/2 (1 µM) and IC₅₀ (2 µM). Data are presented as mean ± SD of three independent experiments. * and ****, p < 0.05 and p < 0.0001, vs. control (one-way ANOVA, Dunnett’s multiple comparison tests).

Figure 9

The assessment of the effect of 5a and 6a on the glycolytic profile of PA-1 tumor cells by measuring the rate of medium extracellular acidification (ECAR). (a,b)—Kinetic curves. (c,d)—Calculated parameters of glycolytic function (glycolysis level and glycolytic capacity). Data are presented as means ± SEM. *, ** and ****, p < 0.05; p < 0.01 and p < 0.0001, vs. control (one-way ANOVA, Dunnett’s multiple comparison tests).