Study On The Synthesis And Structure-activity Relationship Of Benzimidazole PARP-1 Inhibitors

Poly ADP-ribose polymerases（PARPs）,a protein family consisting of 17 subtypes,were significant enzymes which role in DNA damage repair process.It also plays an important role in a wide range of biological processes such as apoptosis and transcriptional regulation,maintaining genome stability,cell cycle progression and chromatin dynamics regulation.PARP-1,the most abundant and well-characterized member of the PARP family,was involved in the base excision repair（BER）pathway of eukaryotic cells to repair DNA single-strand breaks.Once the DNA damaged PARP-1 would be activated to catalyze the conversion of nicotinamide adenine dinucleotide（NAD⁺）to nicotinamide and ADP-ribose,transfer the ADP-ribose unit to the nuclear receptor protein and formed poly（ADP-ribose）on the substrate protein,which was essential for the transferring process of DNA repair and maintaining genome stability.Up to now,four PARP inhibitors were available on the market,such as Olaparib,Rucaparib,Niraparib and Talazoparib and many inhibitors were candidate in clinical trials,such as Veliparib,and Fluzoparib.Although tremendous progress has been made in the research of PARP-1inhibitors,there were still many shortcomings such as serious toxicity in combination with chemotherapy drugs,in vivo side effects or poor pharmacodynamics and pharmacokinetic properties.Therefore,This paper uses 1H-benzo[d]imidazole-4-carboxamide as the skeleton to design and synthesize a series of2-（4-（4-acetylpiperazine-1-carbonyl）phenyl）-1H-benzo[d]imidazole-4-car-boxamide derivatives have designed and synthesized as novel and effective PARP-1 inhibitors.In the synthesis of the target compound,the commercially available 3-nitrophthalic anhydride is used as the raw material,and it is sequentially generated by amino ring opening,Hoffman rearrangement reaction,amidation reaction,reduction reaction,and nucleophilic addition-oxidation.Benzimidazole ring and acid amine condensation reaction to obtain the target compound.The structure was confirmed by ¹H NMR,¹³C NMR,MALDI-TOF MS and Elemental analysis.These derivatives were evaluated for their PARP-1 inhibitory activity and cellular inhibitory against BRCA-1 deficient cells（MDA-MB-436）and wild cells（MCF-7）using PARP kit assay and MTT method.The results indicated that compared with other heterocyclic compounds,furan ring-substituted derivatives 14n-14q showed better PARP-1 inhibitory activity.Among this derivatives,compound 14p has strong effect on PARP-1 enzyme(IC₅₀=0.023μM)and MDA-MB-436cancer cell(IC₅₀=43.56±0.69μM),which was close to Olaparib.Finally,the molecular docking method was used to explore the binding mode of compound 14p and PARP-1,and implied that the formation of hydrogen bond was essential for PARP-1 inhibition activities.The results of this experiment can also indicate that the introduction of strong electronegative groups or halogen atoms in the side chain of benzimidazole is beneficial to improve the PARP-1 enzyme inhibitory activity of the compound,which lays a theoretical foundation for the further development and research of new PARP-1 inhibitors.