Synthesis and evaluation of 9-benzylideneamino derivatives of homocamptothecin as potent inhibitors of DNA topoisomerase I

Friedlӓnder's synthesis of quinolines as a pivotal step in the development of bioactive heterocyclic derivatives in the current era of medicinal chemistry

In the current scenario of medicinal chemistry, quinoline plays a pivotal role in the design of new heterocyclic compounds with several pharmacological properties, so the search for new synthetic methodologies and their application in drug discovery has been widely studied. So far, many procedures have been performed for the preparation of quinoline scaffolds, among which Friedländer quinoline synthesis plays an important role in obtaining these heterocycles. The Friedländer reaction involves condensation between 2-aminobenzaldehydes and keto-compounds. The quinoline nucleus, once obtained through the Friedländer synthesis, has been extensively modified so that these derivatives can exhibit a large number of biological activities such as anticancer, antimalarial, antimicrobial, antifungal, antituberculosis, and antileishmanial properties. In this work, the focus is on the applicability of the Friedländer reaction in the synthesis of various types of bioactive heterocyclic quinoline compounds, which to date has not been reported in the context of medicinal chemistry. The main part of this review selectively focuses on research from 2010 to date and will present highlights of the Friedländer quinoline synthesis procedures and findings to address biological and pharmacological activities.

Development of newly synthesised quinazolinone-based CDK2 inhibitors with potent efficacy against melanoma

Inhibiting Cyclin-dependent kinase 2 (CDK2) has been established as a therapeutic strategy for the treatment of many cancers. Accordingly, this study aimed at developing a new set of quinazolinone-based derivatives as CDK2 inhibitors. The new compounds were evaluated for their anticancer activity against sixty tumour cell lines. Compounds 5c and 8a showed excellent growth inhibition against the melanoma cell line MDA-MB-435 with GI% of 94.53 and 94.15, respectively. Cell cycle analysis showed that compound 5c led to cell cycle cessation at S phase and G2/M phase revealing that CDK2 could be the plausible biological target. Thus, the most cytotoxic candidates 5c and 8a were evaluated in vitro for their CDK2 inhibitory activity and were able to display significant inhibitory action. The molecular docking study confirmed the obtained results. ADME study predicted that 5c had appropriate drug-likeness properties. These findings highlight a rationale for further development and optimisation of novel CDK2 inhibitors.

A comprehensive review of topoisomerase inhibitors as anticancer agents in the past decade

The topoisomerase enzymes play an important role in DNA metabolism, and searching for enzyme inhibitors is an important target in the search for new anticancer drugs. Discovery of new anticancer chemotherapeutical capable of inhibiting topoisomerase enzymes is highlighted in anticancer research. Therefore, biologists, organic chemists and medicinal chemists all around the world have been identifying, designing, synthesizing and evaluating a variety of novel bioactive molecules targeting topoisomerase. This review summarizes types of topoisomerase inhibitors in the past decade, and divides them into nine classes by structural characteristics, including N-heterocycles compounds, quinone derivatives, flavonoids derivatives, coumarin derivatives, lignan derivatives, polyphenol derivatives, diterpenes derivatives, fatty acids derivatives, and metal complexes. Then we discussed the application prospect and development of these anticancer compounds, as well as concluded parts of their structural-activity relationships. We believe this review would be invaluable in helping to further search potential topoisomerase inhibition as antitumor agent in clinical usage.

An Efficient One-Pot Synthesis of Densely Functionalized Fused-Quinolines via Sequential Ugi4CC and Acid-Mediated Povarov-Type Reaction

A divergent synthesis of fused-quinolines has been explored by performing Ugi four-component condensation and sulfuric acid promoted deprotection/Povarov-type reaction in one-pot. The process involves Ugi condensation of propiolic acids, aldehydes/ketones, aminoaldehyde acetals and isocyanides followed by sulfuric acid promoted deprotection and Povarov-type reaction with anilines in ethanol. This method enables straightforward access to the structurally diverse 2,3-dihydro-1H-pyrrolo[3,4-b]quinolin-1-ones (DHPQ), 3,4-dihydrobenzo[b][1,6]naphthyridin-1(2H)-ones (DHBN), and 2,3,4,5-tetrahydro-1H-azepino[4,3-b]quinolin-1-ones (THAQ), starting from readily available starting materials.

Discovery of 7-Methyl-10-Hydroxyhomocamptothecins with 1,2,3-Triazole Moiety as Potent Topoisomerase I Inhibitors

Homocamptothecin is emerging as an important topoisomerase I inhibitor originating in natural product camptothecin. We report the modifications and SAR of homocamptothecin on position C10 to develop potent topoisomerase I inhibitors for anticancer drug discovery. Based on click chemistry, twenty-one 1,2,3-triazole-substituted homocamptothecin derivatives were readily synthesized in two steps. For A549, cycloalkyl- and alkyl-substituted compounds 6j, 6l, and 6o revealed highly antiproliferative inhibitory activities with IC50 value of 30, 30, and 50 nm, respectively. In addition, cyclopropyl 6j exhibited greater Topo I inhibitory activity than 20(S)-Camptothecin, which indicated suitability for further drug development.

Perspectives on biologically active camptothecin derivatives

Camptothecins (CPTs) are cytotoxic natural alkaloids that specifically target DNA topoisomerase I. Research on CPTs has undergone a significant evolution from the initial discovery of CPT in the late 1960s through the study of synthetic small-molecule derivatives to investigation of macromolecular constructs and formulations. Over the past years, intensive medicinal chemistry efforts have generated numerous CPT derivatives. Three derivatives, topotecan, irinotecan, and belotecan, are currently prescribed as anticancer drugs, and several related compounds are now in clinical trials. Interest in other biological effects, besides anticancer activity, of CPTs is also growing exponentially, as indicated by the large number of publications on the subject during the last decades. Therefore, the main focus of the present review is to provide an ample but condensed overview on various biological activities of CPT derivatives, in addition to continued up-to-date coverage of anticancer effects.

Synthesis and biological assays of 9-(acylamino) homocamptothecins as DNA topoisomerase I inhibitors

In an effort to improve the stability of homocamptothecin and reduce the toxicity, novel homocamptothecin analogs with acylamino groups at C(9) were designed and synthesized. The cytotoxic activities of all the synthetic compounds against three cancer cell lines were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, and irinotecan was used as reference compound. Compound 7c with a piperidinylacetamido group and 10a with phenylacetamido group at C(9) showed potent activities both in vitro and in vivo. In addition, they also revealed remarkable topoisomerase I inhibitions which were exhibited with well-established bonds with amino acid residues Arg364 and Asp533 in the active pocket. On the basis of the biological activities, 7c and 10a would be potential candidates for further studies.

Synthesis and Pharmacological Evaluation of Novel Homocamptothecin-Dihydropyridine Derivative Conjugates as Potent Topoisomerase I Inhibitors

Homocamptothecins (hCPT) represent a new generation of antitumour agents targeting DNA topoisomerase I. The expanded seven-membered lactone E-ring that characterizes hCPT enhances the plasma stability of the drug and reinforces the inhibition of topoisomerase I (Topo I) compared with conventional six-membered CPT. In an attempt to improve the antitumour activity of hCP, a series of novel hCPT derivatives conjugating with dihydropyridine derivates were designed and synthesized based on a synthetic route that couples 7-formylhomocamptothecin with different dihydropyridine derivates. Most of the synthesized compounds exhibited good cytotoxic activity on tumour cell line A549, MDA-MB-435, and HCT116. Furthermore, this class of compounds showed superior Topo I inhibition activity comparable to or higher than CPT.