Novel Telomerase Inhibitors:Design,Synthesis,in Vitro Anticancer Activity Evaluation And Structure-Activity Relationship Studies Of 2-Phenyl-4H-Chromone Derivatives

Telomerase have been highly expressed in most tumor cells to varying degrees.Reactivation of telomerase is an important step in cell immortalizationan that is tumorigenesis.It has always been of interest to design,synthesize and screen novel compounds with highly inhibitory telomerase activity for cancer treatment.Based on the previous work of the research group,we designed and synthesized two series of A and B,a total of sixty six 2-phenyl-4H-chromone derivatives containing amide and 1,3,4-oxadiazole moieties as potential telomerase inhibitors.All the title compounds were confirmed by1 H NMR,13 C NMR and HRMS.Among them,the structure of compounds A11 and B8 were further confirmed by single crystal X-ray diffraction.The TRAP-PCR-ELISA assay was used to determine the inhibitory effect of all the title compounds on telomerase.The results showed that most of the title compounds possessed excellent inhibitory activities on telomerase,among which compounds A2,A5,A16,A20,A27,A33,B27 and B33 displayed higher telomerase inhibitory activities(IC₅₀ < 1 μM),with IC₅₀ values of 0.77,0.81,0.62,0.92,0.32,0.44,0.51 and 0.97 μM,which were better than positive control staurosporine(IC₅₀ = 6.41μM)and comparable to the positive control BIBR1532(IC₅₀ = 0.29 μM).Antiproliferative activities of some of compounds against these five cancer cell lines（A375 human melanoma cells,MDA-MB-231 human breast cancer cells,MGC-803 human gastric cancer cells,SMMC-7721 human liver cancer cells,and SGC-7901 human gastric cancer cells）in vitro was determined by MTT assay.It was observed thatcompound A33,which possessed highly efficient telomerase inhibitory activity,demonstrated moderately potent anticancer activity against all five cancer cell lines,with IC₅₀ values of 11.21,9.89,8.76,9.67 and 10.01 μM,respectively.And this compound was not obviously toxic towards L-02（human immortalized normal liver cells）,with IC₅₀ of 2.3 m M.Flow cytometric analysis results revealed compound A33 could induce MGC-803 cells apoptosis by arresting cell cycle at G2/M phase in a dose-dependent manner.In addition,the results of Western blot experiments indicated that compound A33 reduced the expression of Dyskerin-NOP10-NHP2 trimer protein,a core component of telomerase in a concentration-dependent manner.Based on the telomerase inhibitory activities data of the title compounds,the preliminary structure-activity relationships（SARs）was summarized.The methoxy substitution at the R¹ position was conducive to the improvement of telomerase inhibitory activity.Para substitution of the phenyl ring at the R² position generally exhibited stronger telomerase inhibitory activity.The para and ortho positions of the phenyl ring at the R² position were substituted by halogens,increasing the inhibition of telomerase with the increase of electronegativity（F > Cl > Br）.In addition,replacing the benzene ring at the R² position with an aromatic fused ring,aromatic heterocycle,and other substituents also had an important effect on telomerase inhibition.In particular,compound A33 obtained by replacing the phenyl group with a styryl group significantly increased the telomerase inhibitory activity.