Synthesis of Novel Phthalazinedione-Based Derivatives with Promising Cytotoxic, Anti-bacterial, and Molecular Docking Studies as VEGFR2 Inhibitors

Abstract

The parent ester methyl-3-[2-(4-oxo-3-phenyl-3,4-dihydro-phthalazin-1-yloxy)-acetylamino] has 18 compounds. The starting material for alkanoates, their corresponding hydrazides, hydrazones, and dipeptides were produced by chemoselective O-alkylation of 2-phenyl-2,3-dihydrophthalazine-1,4-dione with ethyl chloroacetate(4-oxo-3-phenyl-3,4-dihydro-phthalazin-1-yloxy) acetic acid methyl ester. The starting ester was hydrazinolyzed, then azide coupled with amino acid ester hydrochloride to produce several parent esters, and then hydrazinolyzed to produce parent hydrazides. These hydrazides were used to make a series of dipeptides by reacting them with amino acid ester hydrochloride under azide coupling conditions, and they were also condensed with a number of aldehydes to make the hydrazones. These derivatives were subjected to cytotoxicity against HCT-116 and MDA-MB-231 cells and anti-bacterial and molecular docking studies. Results indicated that the tested compounds, especially 7c and 8b with the phenyl phthalazinone moieties, had promising cytotoxicity against the HCT-116 cells with IC₅₀ values of 1.36 and 2.34 μM, respectively. Additionally, the promising compounds 7c and 8b exhibited poor cytotoxicity against WISH cells with much higher IC₅₀ values, so they were safe against normal cells. Compound 8c exhibited potent anti-bacterial activity with inhibition zones of 12 and 11 mm against Staphylococcus aureus and Escherichia coli, respectively. The molecular docking results of compounds 7c and 8b revealed a good binding disposition and the ligand-receptor interactions like the co-crystallized ligand of the VEGFR2 protein, which may be the proposed mode of action. Finally, compounds 7c and 8b exhibited good ADME pharmacokinetics with good drug-likeness parameters. Hence, detailed studies for the mechanism of action of such compounds are highly recommended for the development of new potent anti-cancer and anti-bacterial agents.

Figure 1

(A) Some common phthalazine-based compounds are used as anti-cancer drugs. (B) Some common phthalazine-based compounds as VEGFR2 inhibitors. (C) Design strategy for the synthesized compounds.

Scheme 1. Synthesis of Ester 2 and Corresponding Hydrazide 3 from Phthalazinedione

Scheme 2. Synthesis of Methyl-3-[2-(4-oxo-3-phenyl-3,4-dihydro-phthalazin-1-yloxy)-acetylamino]alkanoate 5a–c and Their Corresponding Hydrazides 6a–c

Scheme 3. Synthesis of Dipeptides 7a–i from Corresponding Hydrazides 6a–c

Scheme 4. Synthesis of Schiff’s Bases 8a–i from Corresponding Hydrazides 6a–c

Scheme 5. Synthesis of Methyl-4-[2-(4-oxo-3-phenyl-3,4-dihydro-phthalazin-1-yloxy)-acetylamino]-benzoate (9)

Figure 2

Cytotoxic activity of compounds 7c and 8b against HCT-116 and normal WISH cells. Upper panel: microscopy investigation after 48 h of incubation (40× magnification); lower panel: percentages of cell viabilities with increasing concentrations against the three tested cells.

Figure 3

Binding disposition of the co-crystallized ligand (orange-colored) and the docked compound (green-colored) of (A) 7c and (B) 8b toward the VEGFR2 protein (1YWN).

Figure 4

BOILED-Egg model for compounds (A) 7c and (B) 8b using the SwissADME. “Points located in the BOILED-Egg’s yolk are molecules predicted to passively permeate through the blood–brain barrier, while points located in the BOILED-Egg’s white are molecules predicted to be passively absorbed by gastrointestinal tract”.