Studies On Synthesis And Biological Evaluation Of Coumarin And Purine Nucleoside Derivatives

Structural modification and transformation of natural products is an important approachfor the discovery of new drugs. Coumarins and purine nucleosides are two very importanttypes of natural bioactive compounds. Coumarins, distributed in nature, possess a varietyof biological activities. Recently, widespread attention has been draw to modification andrenovation of the coumarins. Purine nucleosides and their analogues, an important class ofbiologically active compounds, play so important role in many fields, especially inmedicine, that current research has been increasingly focused on the discovery andsynthesis of novel compounds with antiviral and antitumor properties. Structuremodification and transformation based on coumarins and purine nucleosides has importantsignificance for the discovery of new drugs. Therefore, firstly, series of coumarins weresynthesized with the introduction of different functional groups, including methyl,amantadine, pyrazole, allyl etc., and then their antioxidant and antitumor activities weretested in vitro in this essay. Then series of6-(het) aryl-7-deazapurine nucleosides weresynthesized based on modification and their biological activity were also evaluated invitro. The innovative research results achieved are as follows:(1) A furanocoumarin xanthotoxol (Xan), with variety of physiological activity, waschosen as lead compound. Its4-methyl and4,9-dimethyl analogues, MXan and DMXan,were synthesized by the multi-step reaction starting from simple starting materials4-methyl-7-hydroxycoumarin, and the synthetic route was also discussed. Different invitro antioxidant models, such as2,2′-diphenyl-1-picrylhydrazyl radical (DPPH),2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+), galvinoxylradical, β-carotene-bleaching in chemistry systems and Cu2+/glutathione (GSH)-mediatedand2,2′-azobis(2-amidinopropane hydrochloride)(AAPH)-induced oxidation of DNA inthe chemical simulation biological systems were employed to investigate the antioxidant capacity of Xan, MXan and DMXan. The results showed that methyl attaching toxanthotoxol did not affect its ability to protect linoleic acid against autoxidation and toinhibit Cu2+/GSH-induced oxidation DNA, but decreased its ability to scavenge ABTS+and DPPH, and to protect DNA against AAPH-induced oxidation. The hydroxyl group at8-position played a major role in the antioxidant of xanthotoxol, and the methyl at4-position and9-position exhibited prooxidant properties to a certain extent.(2) Amantadine pharmacophore was introduced into xanthotoxol. Three psoralenderivatives AXan, AMXan and ADMXan modified by amantadine were synthesizedthrough three simple and efficient reactions. The MTT test revealed that Xan, MXan andDMXan exhibited certain inhibition against human lung cancer cell line A549andNCI-H460. AXan, AMXan and ADMXan enhanced the inhibition capacity against the twocancer cell lines, having a moderate inhibitory activity on A549, with IC50value around40μM.(3) A series of7-hydroxycoumarin derivatives containing4,5-dihydropyrazole moietywere synthesized by introducing active pyrazole ring into coumarin skeleton, and thesynthesis was also discussed. Dynamics equations were introduced into the antioxidantsevaluation systems to quantitatively study the antioxidant activity of these4,5-dihydropyrazole coumarins. Test results showed that the two hydroxyl groups ortho toeach other in the benzene ring of4,5-dihydropyrazole coumarins possessed strongercapacity to trap DPPH and protect DNA against AAPH-induced oxidation than that of twohydroxyl groups meta to each other. The N-H in position1-N-unsubstituted4,5-dihydropyrazole ring could also enhance ability to scavenge radicals and to protectDNA. These seven4,5-dihydropyrazole coumarins all could inhibit the oxidation of DNAvia slowing down the rate of product of TBARS and give inhibition time in the process,which were all higher than positive control Xan.3b and4a were two novel and promisingantioxidants suitable for further development.(4)3-ArylCoumarins was chosen for study and series of7and8-substituted3-arylcoumarins were synthesized from simple raw materials2,4-dihydroxybenzaldehyde and substituted phenyl acetic acid through several efficient reactions. The MTT test revealed that the novel3-arylcoumarins could inhibits HeLa cells moreobviously, in which compounds9a,9b,10a and10b, exhibited good inhibitory activity onHeLa cells (IC₅₀=13.50¹7.66μM). Introducing allyl to8-position of3-arylcoumarinswas favorable to improve the activity for inhibiting human cancer cell and the methoxy at7-position may be adverse unfavorable for maintaining the antitumor activity againstSK-HEP-1, HepG2and SGC7901cell lines.(5) Xylocydine, a purine nucleosides CDKs inhibitor, was chosen as leading compoundand6-(het) aryl-7-deazapurine nucleosides were synthesized via base modification. Aroute of syntheses of6-(het) aryl-7-deazapurine nucleosides with tetracyanoethylene and L(-)-xylose as starting molecules though multistep reaction was developed and theconditions of key Suzuki reaction in the synthetic route was also optimized. Forty six newcompounds were obtained, including thirty target compounds and sixteen intermediateproducts. The results of CDK1/Cyclin B1and CDK2/Cyclin A2inhibitory assay of theobtained compounds indicated that three purine nucleoside derivatives,3h,3i and3jshowed significant activity on CDK2/Cyclin A2, with IC₅₀value of4.6μM,4.8μM and55μM respectively. Although the inhibition activity of3h,3i and3j decreased to comparewith the xylocydine, the selectivity to CDK2/Cyclin A2has been increased. Those threecompounds all induced G1/S phase arrest in Human epithelial carcinoma cell line (HeLa),and the results suggested they may inhibit CDK2activity in vitro. Furthermore, molecularmodeling study was conduct to understand the structural features of CDK2inhibitors, thethree novel CDK2inhibitors3h-j showed high docking scores. On the other hand,compound3g was found exhibiting certain inhibitory activity against four kinds of humancancer cells (A549, HeLa, SK-HEP-1, and MCF-7) in the MTT method filtering on abovetarget compounds. The target compounds DMBPN and DPBPN were obtained by furthermodification based on3g and the synthetic route was optimized with a "one pot" method.The result of antitumor in vitro by MTT method showed that DMBPN and DPBPNimproved the inhibitory activity on the above four kinds of cancer cell dramatically.DMBPN had a significant inhibiton on these four types of cells with IC₅₀value under10 μM, among which the inhibitory activity was best for SK-HEP-1, with IC₅₀value of4.13μM.