Design,Synthesis And Preliminary Activity Evaluation Of 6-position Aromatic Substituted Purine Derivatives As CDK2 Inhibitors

Cyclin-dependent kinases(CDKs)are essential kinases that drive cell cycle transformation and transcriptional regulation.Cyclin-dependent kinase 2(CDK2)is engaged in the transformation of S phases and M phases in the cell cycle by phosphorylating related substrates.CDK2 is also involved in many critical physiological processes,such as DNA damage,intracellular transport,protein degradation,signal transduction,and DNA/RNA metabolism and translation.CDK2 and Cyclin A/E,which are highly expressed and abnormally activated in many cancers,widely participate in the malignant proliferation of tumor cells.A variety of cancers show sensitivity to the inhibition of CDK2,CDK2 is considered to be the key target of antitumor drug development.Based on the original pan-CDK inhibitors,a serious of selective CDK2 inhibitors have been found.At present,some CDK2 inhibitors are in clinical trials,providing a new method for tumor treatment.Based on the previous work of CDK inhibitors in our group,we designed a series of 6-position aromatic substituted purine derivatives as CDK2 inhibitors.According to the retrosynthetic analysis,we used 2,6-dichloropurine as the prime material,first protected the purine N-9 with THP group,and then obtained the final product through Suzuki reaction and Buchwald-Hartwig coupling.A total of 52 new compounds were synthesized,including 30 intermediates and 22 target compounds.All target compounds were confirmed by 1H NMR,13C NMR,and HRMS.For the target compounds,we first determined their CDK2 inhibition activity.We found that the CDK2 inhibition activity was significantly improved when the aromatic substituents of purine C-6 were polar groups.For different aromatic amines at the C-2 position of purine,compounds with smaller hydrophobic groups such as 5i,7h,and 7i had better activity,and those with meta-substitution had higher activity than those with para-substitution.Among all the compounds,5i had the best CDK2 inhibitory activity with an IC50 value of 117 nM.Molecular docking of 5i showed that the amino group of its purine C-6 benzylamine could bind into the ATP binding pocket,and form hydrogen bond interaction with Asp145 and Asn132.Besides,this series of compounds showed no activity for CDK7,the inhibition of CDK7 were less than 50%at the concentration of 10 μM.In vitro antitumor cell proliferation assay showed that 5i had IC50 values of 6.22 μM for HCT-116 and 9.37 μM for MDA-MB-231,which were about twice lower than that of R-Roscovitine.In conclusion,we designed and synthesized a series of 6-position aromatic substituted purine derivatives as CDK2 inhibitors based on our previous work.The experimental results showed that these compounds showed potent inhibition of CDK2 activity and antiproliferative activity.This work lays a foundation for the further development of CDK2 inhibitors with better activity and selectivity in our future work.