Design, Synthesis And Antitumor Research Of Novel Taxane Derivatives

Paclitaxel (Taxol), a highly functionalized diterpene natural product isolated from thebark of Pacific yew(Taxus brevifolia) in1960s demonstrated antitumor activity in humanmalignancies. A unique mechanism of paclitaxel as an antimitotic agent is based on itsbinding to the β-tubulin subunit of the tubulin dimer, accelerating their polymerization toresult in stabilized microtubules and resisting to depolymerization back to tubulin. Thiscauses the arrest of the cell division cycle mainly at the G2/M phase resulting in apoptosisthrough the cell-signaling cascade. As a semisynthetic derivative of taxol, docetaxel hasthe same antitumor mechanism with taxol. As two of the most important chemotherapeuticdrugs, taxol and docetaxel are widely used to fight against some types of tumors in clinic.Despite their potent antitumor activity, paclitaxel and docetaxel cause undesirable sideeffects as well as drug resistance. Thus, it is essential to develop new taxane antitumoragents that would have fewer side effects, enhanced activity against various classes oftumors, especially against drug-resistant tumors.Compounds containing aryl isoxazole and quinoline scaffold have received considerable attention because of their wide biological activities, and a number of novelaryl isoxazole or quinoline derivatives were reported to have the antitumor activitydepending on various mechanisms. Meanwhile, some quinoline derivatives have beenreported to possess MDR reversal effect when combined with anticancer drug.The idea of combining different bioactive groups into a compound is popular in drugdesign. Thus, we envisioned that a combination of docetaxel with aryl isoxazole orquinoline moiety into a single molecule might improve the antitumor activity. Therefore,we designed and synthesized a series of novel aryl isoxazole-docetaxel andquinoline-docetaxel derivatives by esterification of C2’-OH or C3’-NH2of docetaxel witharyl isoxazoline carboxylic acids and quinoline acids, and their cytotoxicities againstnormal human tumor cell lines, Hela, SK-OV-3, A549, A2780, MCF-7, and twodrug-resistant tumor cell lines, A2780-MDR and MCF-7-MDR were evaluated by MTTassays in vitro with docetaxel as positive control after exposure of cells to the testedcompounds for72h.1. Design, synthesis and antitumor effect of novel aryl isoxazole-docetaxelderivativesA series of novel aryl isoxazole-docetaxel derivatives were synthesized byintroduction of aryl isoxazole scaffold into C2’-OH or C3’-NH2of docetaxel andcharacterized by1HNMR,13CNMR and HRMS. The cytotoxicities of these compoundsagainst human tumor cell lines were evaluated by MTT assays in vitro with docetaxel aspositive control. The data showed some compounds exhibited similar to better inhibitoryactivities than docetaxel.(1) All the compounds showed better antitumor activities against Hela than docetaxe l, andthe cytotoxicity of1.41h was5times stronger than docetaxel.(2) Compounds1.47A-1.47E exhibited better antitumor activities against A2780thandocetaxel, and the cytotoxicities of1.47A and1.47E were4times stronger thandocetaxel.(3) Compound1.41c showed significant inhibitiory preference to Hela.(4) What’s more, all the compounds showed obvious inhibition against two drug-resistant tumor cell lines. The inhibition of compound1.33g against A2780-MDR was15timesmore potent than docetaxel. Meanwhile, the inhibition of compounds1.41f and1.41hagainst MCF-7-MDR were10times more potent than docetaxel.To further investigate whether the compounds(1.47A-1.47E) have effects oncytoskeleton, we employed immunofluorescence techniques. The results showed thecytoskeleton of A2780were obviously disrupted and displayed the disperse conditionwhen cells were exposed to the tested compounds compared to the integrity of control.The research indicated the introduction of aryl isoxazole scaffold into docetaxel wasimportant to the antitumor activity of docetaxel.2. Design, synthesis and antitumor effect of novel quinoline-docetaxel derivativesA series of novel quinoline-docetaxel derivatives were synthesized by introduction ofquinoline scaffold into C2’-OH of docetaxel and characterized by1HNMR,13CNMR andHRMS. The cytotoxicities of these compounds against human tumor cell lines wereevaluated by MTT assays in vitro with docetaxel as positive control. The data showedmost compounds exhibited similar to better inhibitory activity than docetaxel.(1) All the compounds showed better antitumor activities against Hela than docetaxel, andthe cytotoxicity of2.15f was5times stronger than docetaxel.(2) The cytotoxicity of2.13f against A549was2times stronger than docetaxel, and thecytotoxicities of2.15c and2.15d against A2780were2times stronger than docetaxel.(3) Compounds2.13b,2.13d and2.13e showed significant inhibitiory preference toMCF-7, the inhibition of2.13e was3times stronger than docetaxel.(4) Importantly, some compounds showed potential reversal activity and improve thesensibility of drug-resistant tumor cell lines to docetaxel. Compounds2.13d,2.15dand2.13a,2.13c were found to possess the most potent inhibitory effects among theseanalogues against A2780-MDR and MCF-7-MDR, respectively. The inhibition ofcompound2.13a and2.13c against MCF-7-MDR were20times more potent thandocetaxel.The research indicated that the introduction of quinolyl group into docetaxel couldenhance cytotoxicity and reduce drug-resistance. 3. An efficient synthesis of cabazitaxelCabazitaxel, a semisynthetic taxane possessing the same antitumor mechanism withpaclitaxel and docetaxel, is a7,10-O-dimethylated derivative of docetaxel and approvedby the US Food and Drug Administration (FDA) in2010for the treatment of advancedprostate cancer. There are some synthetic routes to have been reported so far. However,these methods are not suitable for scale-up because of low yield or purification. Wedesigned a convenient four-step procedure with10-DAB as starting material in a43.6%total yield, and purity is to99.28%after recrystallization. The new synthetic route,featuring the preparation of the basic key intermediate3.3, which made the purificationsimpler, just adjusting suitable pH, is suitable for large-scale production and we could get50g scale in our lab currently.