Synthesis and Cytotoxicity of Novel β-Ala-Phthalazine-Based Derivatives as VEGFR2 Inhibitors and Apoptosis-Inducers Against Liver Cancer

Some novel β-Ala-phthalazine derivatives were synthesized from the parent methyl 3-(2-(4-benzyl-1-oxophthalazin-2(1H)-yl) acetamido)propanoate (1). Then, ester 1 underwent hydrazinolysis to produce the hydrazide 2-(4-benzyl-1-oxophthalazin-2(1H)-yl)-N-(3-hydrazineyl-3-oxo propyl) acetamide (2). Under the azide coupling technique, hydrazide 2 formed azide 3 which was further coupled with some amines and amino acid esters hydrochloride to produce the corresponding novel dipeptides 4a–h and 5a–d, respectively. Finally, hydrazide 2 was condensed and/or cyclized with some ketones and/or active methylene compounds resulting in the formation of various derivatives 6a-e. Compounds 2, 6c, and 6d demonstrated significant cytotoxicity, with IC₅₀ values of 1.33, 0.41, and 0.38 μM compared to Sorafenib (IC₅₀ = 2.93 μM). Compounds 6d exhibited potent VEGFR2 inhibition by 97.6% with an IC₅₀ value of 21.9 μM compared to Sorafenib (94.7% and IC₅₀ value of 30.1 μM). The 6d treatment significantly increased apoptotic activity by 23.6-fold, causing a halt in cell proliferation at the G2/M phase. Ultimately, it exhibited a strong affinity for the VEGFR2 protein, with a binding energy of −26.8 Kcal/mol, and it established binding contacts with the crucial amino acids involved in the interaction.