Synthesis of Pyrrolo[3,4- b]pyridin-5-ones via Ugi-Zhu Reaction and In Vitro-In Silico Studies against Breast Carcinoma

Abstract

An Ugi-Zhu three-component reaction (UZ-3CR) coupled in a one-pot manner to a cascade process (N-acylation/aza Diels-Alder cycloaddition/decarboxylation/dehydration) was performed to synthesize a series of pyrrolo[3,4-b]pyridin-5-ones in 20% to 92% overall yields using ytterbium triflate as a catalyst, toluene as a solvent, and microwaves as a heat source. The synthesized molecules were evaluated in vitro against breast cancer cell lines MDA-MB-231 and MCF-7, finding that compound 1f, at a concentration of 6.25 μM, exhibited a potential cytotoxic effect. Then, to understand the interactions between synthesized compounds and the main proteins related to the cancer cell lines, docking studies were performed on the serine/threonine kinase 1 (AKT₁) and Orexetine type 2 receptor (Ox₂R), finding moderate to strong binding energies, which matched accurately with the in vitro results. Additionally, molecular dynamics were performed between proteins related to the studied cell lines and the three best ligands.

Keywords: MCF-7; MCRs; MDA-MB-231; Pyrrolo[3,4-b]pyridin-5-ones; Ugi–Zhu; breast cancer; docking; molecular dynamics.

Scheme 1

Synthesis of pyrrolo[3,4-b]pyridin-5-ones 1a–1k.

Figure 1

Effect of compounds 1a–1k on cell viability of MDA-MB-231 cells. The MDA-MB-231 cell line was exposed to 0, 6.25, 12.5, 25, 50, 100, and 200 µM of the chemical compounds for 48 h. The graphs are representative of the % cell viability concerning the control and are representative of three independent experiments. Statistical significance was calculated by ANOVA and Dunnett, ±SD with values of * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001 indicating statistical significance.

Figure 2

Effect of compounds 1a–1k on the cell viability of MDA-MB-231 cells. Representative phase contrast microscopy images of MDA-MB-231 tumor cells. The cells were treated with different concentrations of the chemical molecules (0, 6.25, 12.5, 25, 50, 100, and 200 µM) or vehicle (DMSO) for 48 h. Images of morphological changes were taken at 48 h with a 10× objective.

Figure 3

Effect of chemical compounds 1a–1k on cell viability of MCF-7 cells. The MCF-7 cell line was exposed to 0, 6.25, 12.5, 25, 50, 100, and 200 µM of the compounds for 48 h. The graphs are representative of the % cell viability concerning the control and are representative of three independent experiments. Statistical significance was calculated by ANOVA and Dunnett, ±SD with values of * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001 considered statistically significant.

Figure 4

Effect of chemical compounds 1a–1k on cell viability of MCF-7 cells. Representative bright-field microscopy images of MCF-7 tumor cells. Cells were treated with different concentrations of the chemical molecules (0, 6.25, 12.5, 25, 25, 50, 100, and 200 µM) or vehicle (DMSO) for 48 h. Images of the morphological changes at 48 h were taken with a 10× objective on an inverted microscope.

Figure 5

Docking results: (A) energy vs. RMSD, (B) docking to Ox₂R, (C) docking to AKT₁.

Figure 6

MD structure equilibrating descriptors for the interactions 1f, 1h, and 1k with AKT₁.

Figure 7

Structural equilibrating descriptors obtained by MD simulations for the interactions 1f, 1h, and 1k with the Ox₂R receptor.

Figure 8

Main interactions between the protein target AKT₁ and compounds 1f, 1h, and 1k. These interactions are represented by the following arrangements: (A) 1f, (B) 1h, and (C) 1k. Color coding: The interactions are visually depicted using circles containing residue names and lines indicating their spatial arrangement. The interaction colors are consistent across both the bar chart and the 2D maps. Green indicates hydrogen bonding interactions, while blue represents hydrophobic interactions. Purple is used for π-stacking interactions, and red is employed for π–cation interactions. The atom–ligand pairs are visually differentiated based on their respective colors. Carbon is represented by the color gray, nitrogen by blue, oxygen by red, and sulfur by yellow.

Figure 9

Main interactions that occur between the protein target Ox₂R and compounds 1f, 1h, and 1k. These interactions are represented by the following arrangements: (A) 1f, (B) 1h, and (C) 1k. Color coding: The interactions are visually depicted using circles containing residue names and lines indicating their spatial arrangement. The interaction colors are consistent across both the bar chart and the 2D maps. Green indicates hydrogen bonding interactions, while blue represents hydrophobic interactions. Purple is used for π-stacking interactions, and red is employed for π–cation interactions. The atom–ligand pairs are visually differentiated based on their respective colors. Carbon is represented by the color gray, nitrogen by blue, oxygen by red, and sulfur by yellow.