Synthesis And Antitumor Activity Of 2-substituted-tetrahydro-β-carboline Compounds

The overexpression of ATP-binding cassette（ABC）efflux transporter,breast cancer resistance protein（BCRP）/ATP-binding cassette subfamily G member 2（ABCG2）contribute to multiple drug resistance（MDR）in several specific cancers,leading to failure of chemotherapy.To conquer MDR acquired by BCRP overexpression several efforts have been made by developing BCRP inhibitors.Tetrahydro-β-carbolines（THβCs）belongs to carboline alkaloids with dearomatized C-ring,which are widely distributed in nature.Their semi-rigid skeleton structure is associated with diverse pharmacological activities.Several research indicated Fumitremorgin C（FTC）,Ko143,and other analogues were found to be remarkable potent BCRP inhibitors.In this thesis,we developed a 2D-QSAR model with appropriate prediction（R2=0.69）based on the efficacy of ABCG2 inhibitors in the ChEMBL database.A series of 1,6,9-trisubstitued-THβC skeleton structures were designed via structural optimization of FTC and predicted by the 2D-QSAR model.1-methyl-6-methoxy-9-propyl-THβC with superior potency became a lead structure by further screening through ADMET property and Lipinski rules.Two novel series of N-2-substitued THβC compounds were designed and prepared dependent on the prediction model results.The inhibitory activity of these compounds was initially evaluated by CCK-8 method in MDA-MB-231 breast cancer cells in vitro.IC50 and cell cycle tests were further conducted with the most active compounds.Finally,the possible mechanism of these inhibitors was demonstrated by molecular docking to observe the specific binding sites between the novel compounds and ABCG2 protein.The details are as follows:1.Dihydro-β-carboline was obtained by 5-methoxytryptamine via acetylation,N-alkylation and Bischler-Napieralski reaction.1-methyl-7-methoxy-9-propyl-THβC skeleton was achieved by reduction reaction.Two series of N-2 substituted with either alkyl or amide THβC including eighteen monomers and ten dimers,were prepared,and their structures were characterized by ¹H-NMR,¹³C-NMR and HPLC-MS.2.The inhibitory activity of these compounds was initially evaluated in MDA-MB-231breast cancer cells through CCK-8 method at 10μM.IC₅₀ was further tested for the compounds with over 80%inhibition.The IC₅₀ values of the most potent novel THβC compounds were as follows:TDA-11:IC₅₀=6.48±0.23μM;TSA-9E:IC₅₀=6.10±0.20μM;THBC:IC₅₀=5.44±0.15μM;TDN-8:IC₅₀=1.58±0.08μM.Cell cycle results indicated that the cells treated by TDA-11,TSA-9E,THβC were arrested in G2/M phase,while those treated by TDN-8 was arrested in G0/G1 phase.3.Structure-activity analysis demonstrated the N-2-substituted-THβCs with theα-βunsaturated amide exhibited inhibitory activity.However the N-2 position was an alkyl or other aryl amide substitution the activity was significantly lower compared to the lead compound;And if the flexible linker contains 8 or 9 carbons,the N2-N2’dimer molecules exhibit strong inhibitory activity..By molecular docking technique,it was shown that compound TDN-8 can effectively bind into the active cavity of ABCG2 protein.In summary,,four highly active THβCs lead compounds were screened by 2D-QSAR modeling,virtual screening,chemical synthesis,and activity testing,and their interactions with ABCG2 protein were further explored by computer simulations.These novel THβCs are valuable ABCG2 inhibitor candidates for further investigation in the preclinical ABCG2inhibition research.And can be used as a reference for the development of tetrahydro-β-carboline antitumor drugs.