Synthesis and biological evaluation of novel 7-acyl homocamptothecins as Topoisomerase I inhibitors

DNA Topoisomerase 1 Structure-BASED Design, Synthesis, Activity Evaluation and Molecular Simulations Study of New 7-Amide Camptothecin Derivatives Against Spodoptera frugiperda

Camptothecin and its derivatives (CPTs) have strong toxicity to eukaryotic cells by targeting their DNA topoisomerase 1 (Top1) protein and have been increasingly explored as potential pesticides for plant protection. However, the detailed structure-binding mechanism of the interactions between CPTs and the insect Top1 protein remains unclear, which significantly hinders the development of novel CPTs as new insecticides. Herein, a series of 7-amide camptothecin analogs based on the binding mode of camptothecin in complex with Top1 (Sf Top1)-DNA from Spodoptera frugiperda cultured cell line Sf9 were designed and synthesized. Fifteen of these compounds exhibited excellent cytotoxic activity (values of IC₅₀ from 2.01 to 6.78 μM) compared with camptothecin (29.47 μM). The molecular simulations revealed the binding mechanism when the camptothecin parent rings were inserting parallel to DNA bases and stabling the ternary complex by π-π stacked and hydrogen-bond interactions, and further suggested that introduction of lipophilic and some electron-withdrawing groups on the amide linkage of camptothecin could be beneficial to its activity via some non-covalent interactions. Furthermore, almost all the synthesized compounds could inhibit the growth of Spodoptera litura larvae strongly (Inhibition rate from 50.20 to 79.05%), superior or comparable to camptothecin (55.69%) after 8 days of exposure. In particular, the compounds 4c, 4d, 4f, and 4j, which presented more than 70% inhibitory activities, were deserved to be developed as potential biorational pesticides. The information described here would be useful for the further design and development of potentially effective pesticides in the field of plant protection.

Formal [5+2] cycloaddition of vinylethylene carbonates to oxazol-5-(4H)-ones for the synthesis of 3,4-dihydrooxepin-2(7H)-ones

Formal [5+2] cycloaddition of vinylethylene carbonates to oxazol-5-(4H)-ones.

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.

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.

Hybrid anticancer 1,2-diazine derivatives with multiple mechanism of action. Part 3

Antitumour chemotherapy is nowadays a very active field of research, DNA targeting drugs being the most widely used group in therapy. The design, synthesis and anticancer activity of a new class of anticancer derivatives with pyrrolo-1,2-diazine and benzoquinone skeleton is presented. The synthesis is direct and efficient, involving an alkylation followed by a [3+2] dipolar cycloaddition. The penta- and tetra-cyclic pyrrolo-1,2-diazine were evaluated for their in vitro anticancer activity against an NCI 60 human tumour cell line panel. The pentacyclic-1,2-diazine exhibit a significant anticancer activity against Non-Small Cell Lung Cancer NCI-H460, Leukemia MOLT-4, Leukemia CCRF-CEM and Breast Cancer MCF7. We hypothesize that these molecules will exert their anticancer activity through multiple mechanisms of action: intercalating the DNA, inhibiting the topoisomerase enzymes and, destroying the DNA strands via electron transfer mechanism. However, the intercalation with the DNA seems to prevail in competition with the others mechanisms.

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.

Bioluminescence imaging of DNA synthetic phase of cell cycle in living animals

Bioluminescence reporter proteins have been widely used in the development of tools for monitoring biological events in living cells. Currently, some assays like flow cytometry analysis are available for studying DNA synthetic phase (S-phase) targeted anti-cancer drug activity in vitro; however, techniques for imaging of in vivo models remain limited. Cyclin A2 is known to promote S-phase entry in mammals. Its expression levels are low during G1-phase, but they increase at the onset of S-phase. Cyclin A2 is degraded during prometaphase by ubiquitin-dependent, proteasome-mediated proteolysis. In this study, we have developed a cyclin A2-luciferase (CYCA-Luc) fusion protein targeted for ubiquitin-proteasome dependent degradation, and have evaluated its utility in screening S-phase targeted anti-cancer drugs. Similar to endogenous cyclin A2, CYCA-Luc accumulates during S-phase and is degraded during G2/M-phase. Using Cdc20 siRNA we have demonstrated that Cdc20 can mediate CYCA-Luc degradation. Moreover, using noninvasive bioluminescent imaging, we demonstrated accumulation of CYCA-Luc in response to 10-hydroxycamptothecin (HCPT), an S-phase targeted anti-cancer drug, in human tumor cells in vivo and in vitro. Our results indicate that a CYCA-Luc fusion reporter system can be used to monitor S-phase of cell cycle, and evaluate pharmacological activity of anti-cancer drug HCPT in real time in vitro and in vivo, and is likely to provide an important tool for screening such drugs.