Privileged Structure-based Design And Synthesis Of Rutaecarpine Analogues And Their Antitumor Activities

Natural products have always been a valuable resource for the development of new drugs due to their diverse structures and broad-spectrum biological activities.It is an important way to research and develop new drugs through chemical synthesis after structural modification and modification of active natural products.As a natural alkaloid containing quinazolinone skeleton with extensive biological activities,rutaecarpine cannot be widely used in clinical practice due to its weak activity and poor generic medicinal properties.Privileged structure-based drug design(PSBDD)is an important theory guiding drug molecular design,privileged structure has the advantages of good drug properties and high druggability,when it is introduced into the drug molecular skeleton,its activity and similar drug properties can be effectively provided,so as to develop new drugs with better therapeutic effects or new therapeutic functions.In this dissertation,in accordance with privileged structure-based drug design,a variety of rutaecarpine analogues were designed and synthesized by replacing privileged structure units,combing with the skeleton migration strategy,as well as evaluation of biological activity in detail.The contents of this dissertation contain the following several chapters:Chapter I: In the review part,the synthesis and biological activities of rutaecarpine analogues were reviewed.Chapter II: Phthalazine[1,2-b]quinazolinone derivatives were synthesized by our previous work,which is a continuation and further investigation for anti-tumor mechanism in this chapter.p53 inactivation is a clinically defined characteristic for cancer treatment-nonresponsiveness.It is therefore highly desirable to develop anticancer agents by restoring p53 function.Herein the synthesized phthalazino[1,2--b]-quinazolinones were discovered as p53 activators in bladder cancer cells.10-Bromo-5-(2-dimethylamino-ethylamino)-phthalazino[1,2-b]-quinazolin-8-one(5da)was identified as the most promising candidate in view of both its anticancer activity and mechanisms of action.5da exhibited strong anticancer activity on a broad range of cancer cell lines and significantly reduced tumor growth in xenograft models at doses as low as 6 mg/kg.Furthermore,5da caused cell cycle arrest at S/G2 phase,induced apoptosis,changed cell size,and led to cell death by increasing the proportion of sub-G1 cells.Molecular mechanism studies suggested that accumulation of phospho-p53 in mitochondria after 5da treatment resulted in conformational activation of Bak,thereby evoking cell apoptosis,finally leading to irreversible cancer cell inhibition.Our present studies furnish new insights into the molecular interactions and anticancer mechanisms of phospho-p53-dependent quinazolinone compound.Chapter III: Compound 5b,was synthesized by our research group based on the strategy of structural optimization of cryptolepine and aromathecin natural products and identified as the most promising candidate in view of its anticancer activity.Molecular mechanism studies suggested that 5b not only could strongly bind to G-quadruplex,but intercalate into supercoil DNA and resulted in significant DNA double-strand break as well.Furthermore,5b caused cell cycle arrest at S/G2 phase and induced apoptosis.After treatment with 5b,pro-apoptotic proteins were up-regulated,anti-apoptotic proteins were down-regulated,and the effector Caspase-3/9 was activated to initiate apoptosis.The anticancer activity of 5b was finally validated in MGC-803 xenograft tumor model with tumor growth inhibition(TGI)up to 53.2%,while displaying no obvious toxicity.Taken together,these results suggest that 5b may be a potential candidate of cytotoxic antineoplastic drugs for cancer therapy.Chapter IV: 3-(Benzo[d]oxazol-2-yl)-4-aminoquinoline derivatives were designed and synthesized as novel Topoisomerase I(Topo I)inhibitors for antitumor studies.Among all the prepared compounds,structural optimization led to the identification of the most potent compound 5c,3-(benzo[d]oxazol-2-yl)-7-methyl-4--(3-dimethylaminopropyl)aminoquinoline.However,compound 6c which bearing the dimethylaminoethyl side chain and exhibiting low antiproliferative activity.To investigate the difference in mechanism mode of anticancer,compounds 5c and 6c were chosen for further bioactivity investigation.Further molecular mechanistic studies suggested that 5c could interact with DNA to induce Topo I inhibition,thereby evoking S/G2 phase cell cycle arrest resulting in cell apoptosis.The efficiency in vivo of 5c was also carried out on MGC-803 xenograft nude mice,and the relative tumor inhibition ration was up to 31.7% at 20 mg/kg without noticeable weight loss.On the contrary,compound 6c had no significant contribution to the antitumor activity.Collectively,the information gained by our study provides a reference toward discovering novel Topo I-targeted anti-cancer agents and an insight for further development of more active quinoline anti-cancer agents.Chapter V: Thirty-six of 3-(benzo[d]thiazol-2-yl)quinolin-4(1H)-one derivatives had been designed,synthesized and characterized,as well as the anticancer activity in vitro and in vivo were analyzed.In screening their in vitro activity,we found that most of the compounds exhibited effective toxicity on the cancer cell lines,and some of the compounds were ability to induce elevated ROS and ER stress response through mitochondrial dysfunction result in cytoplasmic vacuolation ultimately causes paraptosis in hepatoma carcinoma cells.The potent compound 6ah was screened out via structure-activity relationship analysis,which profoundly facilitated paraptosis cell death and induced Caspase-independent apoptosis simultaneously.Further investigation,flow cytometry analysis results demonstrated that 6ah could arrest the cell cycle at G2/M phase and induce apoptosis in a dose-dependent manner.Overall,our findings provide novel insights into the molecular basis of paraptosis,as well as an alternative therapeutic strategy for treating conventional-therapy-resistant cancer through the induction of paraptosis.In a word,under the guidance of privileged structure theory,based on the structural modification of rutaecarpine,four series of rutaecarpine analogies were designed and synthesized in combination with pharmacophore.Our results are expected to provide reference information and lay a theoretical foundation for the development and research of new antitumor drug candidates.