Semisynthesis, Biological Activity, and Molecular Modeling Studies of C-Ring-Modified Camptothecins

Recent Advancements in the Synthesis of α-fluoroalkylated Azine-derived Heterocycles through Direct Fluorination

The review highlights recent advancements in the synthesis of α-fluoro and α,α- difluoroalkylated azines, focusing on two main approaches. The first approach involves nucleophilic deoxofluorination, wherein α-hydroxy- or α-oxoalkylated azines are treated with diethylaminosulfur trifluoride or other S-F reagents to introduce fluorine atoms. The second approach employs direct electrophilic benzylic fluorination, whereby alkylazines undergo fluorination using N-F reagents. Both methods provide flexibility in designing and synthesizing fluoroalkylated heterocycles.

New 5-Substituted SN38 Derivatives: A Stability Study and Interaction with Model Nicked DNA by NMR and Molecular Modeling Methods

The new 5-substituted SN-38 derivatives, 5(R)-(N-pyrrolidinyl)methyl-7-ethyl-10-hydroxycamptothecin (1) and its diastereomer 5(S) (2), were investigated using a combination of nuclear magnetic resonance (NMR) spectroscopy and molecular modeling methods. The chemical stability, configuration stability, and propensity to aggregate as a function of concentration were determined using 1H NMR. The calculated self-association constants (Ka) were found to be 6.4 mM-1 and 2.9 mM-1 for 1 and 2, respectively. The NMR experiments were performed to elucidate the interaction of each diastereomer with a nicked decamer duplex, referred to as 3. The calculated binding constants were determined to be 76 mM-1 and 150 mM-1 for the 1-3 and 2-3 complexes, respectively. NMR studies revealed that the interaction between 1 or 2 and the nicked decamer duplex occurred at the site of the DNA strand break. To complement these findings, molecular modeling methods and calculation protocols were employed to establish the interaction mode and binding constants and to generate molecular models of the DNA/ligand complexes.

Design and synthesis of novel conformationally constrained 7,12-dihydrodibenzo[b,h][1,6] naphthyridine and 7H-Chromeno[3,2-c] quinoline derivatives as topoisomerase I inhibitors: In vitro screening, molecular docking and ADME predictions

Novel non-camptothecin (non-CPT) class of conformationally constrained, hitherto unknown 7,12-dihydrodibenzo[b,h][1,6] naphthyridine and 7H-Chromeno[3,2-c] quinoline derivatives have been designed, synthesized and evaluated for anti-cancer activity. In vitro anti-proliferation evaluation against human cancer cell lines (A549 and MCF-7) exhibited significant cytotoxicity. Among the derivatives (8-24), 8 (IC₅₀ 0.44 μM and IC₅₀ 0.62 μM) and 12 (IC₅₀ 0.69 μM and IC₅₀ 0.54 μM) were identified as the most promising candidate against A-549 and MCF-7 cancer cell lines respectively. Topo I inhibitory activity of 8 and 12 suggested that, they may be developed as potential anti-cancer molecules in future and rationalized by docking analysis with effective binding modes. Further, in silico ADME prediction studies of all derivatives were found promising, signifying the drug like properties. In precise, the present investigation displays a new strategy to synthesize and emphasis on anticancer activities of conformationally constrained dibenzo[b,h][1,6] naphthyridine derivatives and Chromeno[3,2-c] quinoline derivatives in the context of cancer drug development and refinement.

New camptothecin derivatives for generalized oncological chemotherapy: Synthesis, stereochemistry and biology

Derivatives of SN38 were synthesized that were either monosubstituted at C-5 or C-9 or disubstituted at both C-5 and C-9. Substitution to C-5 led to the generation of pairs of diastereomers (2c-2 h) in a one-pot reaction and was readily separable by HPLC. The absolute configurations of C-5 were established by electronic circular dichroism experiments. Compounds were tested in vitro against human cancer cell lines as well as a normal cell line. The impact of compounds 2a-2j on cancer cells is significant and the IC₅₀ values against the normal cell line are several times higher than that of SN38. Using the Mannich reaction we obtained a new innovative group of derivatives with unique biological properties that preserves the high cytotoxicity in cancer cells and eliminates the acute toxicity to non-neoplastic cells, which can be considered a breakthrough in chemotherapy with the use of topoisomerase I inhibitors from the camptothecin family.

Exploring the behavior of the NFSI reagent as a nitrogen source

The diverse biological activities of nitrogen-containing compounds make the construction of the C-N bond of great importance. As N-fluorobenzenesulfonimide, one of the most abundant chemical feedstock, has a dual behaviour, i.e. as an electrophilic fluorination and amidation source, it attracts the attention of synthetic chemists for exploitation. This review comprehensively summarizes the significant progress of the efficient and mild amidation reactions, with an emphasis on approaches for the generation of nitrogen-centered intermediates, related mechanisms and new synthetic chemistry methods that offer opportunities to overcome obstacles in pharmaceutical applications. In this perspective, we discuss the developments in the amidation reaction using NFSI in the past decade. We discuss the recent progress, challenges and future outcomes in the area of amidation chemistry using commercially available NFSI.

Development of an enzyme‑linked immunosorbent assay for camptothecin

The use of camptothecin and its analogues has increased in clinical settings and in agriculture. Therefore, camptothecins and their derivatives, metabolites and degradation products are frequently found in the environment. Therefore, it is important to develop an ELISA for the quantification of camptothecins in human plasma, plants, animal tissues and other matrices. The present study developed a novel competitive indirect ELISA for camptothecin using a monoclonal antibody (MAb). In total, two haptens and various carrier proteins were tested to select the most suitable immunogen for the production of MAbs against camptothecin. Hapten 1 conjugated with keyhole limpet hemocyanin was selected for the preparation of MAb 5A3, and was used to establish a competitive indirect ELISA for camptothecin. A total of three derivatives of camptothecin used in clinical practice were examined. Topotecan showed an IC₅₀ value of 0.68 µg/ml with a detection limit of 0.19 µg/ml, belotecan showed an IC₅₀ value of 0.87 µg/ml with a detection limit of 0.22 µg/ml and irinotecan showed an IC₅₀ value of 2.85 µg/ml with a detection limit of 0.47 µg/ml. The cross-reactivity results suggested that the assay developed in the present study possessed a high sensitivity to camptothecin. Therefore, this immunoassay technique may be suitable for monitoring the levels of camptothecin in compound analysis, clinical applications, and analyses of food and environmental samples.

A Novel Camptothecin Derivative 3j Inhibits Nsclc Proliferation Via Induction of Cell Cycle Arrest By Topo I-Mediated DNA Damage

OBJECTIVE

The aim of this study is to investigate the inhibitory effect of camptothecin derivative 3j on Non-Small Cell Lung Cancer (NSCLCs) cells and the potential anti-tumor mechanisms.

BACKGROUND

Camptothecin compounds are considered as the third largest natural drugs which are widely investigated in the world and they suffered restriction because of serious toxicity, such as hemorrhagic cystitis and bone marrow suppression.

METHODS

Using cell proliferation assay and S180 tumor mice model, a series of 20(S)-O-substituted benzoyl 7- ethylcamptothecin compounds were screened and evaluated the antitumor activities in vitro and in vivo. Camptothecin derivative 3j was selected for further study using flow cytometry in NSCLCs cells. Cell cycle related protein cyclin A2, CDK2, cyclin D and cyclin E were detected by Western Blot. Then, computer molecular docking was used to confirm the interaction between 3j and Topo I. Also, DNA relaxation assay and alkaline comet assay were used to investigate the mechanism of 3j on DNA damage.

RESULTS

Our results demonstrated that camptothecin derivative 3j showed a greater antitumor effect in eleven 20(S)-O-substituted benzoyl 7-ethylcamptothecin compounds in vitro and in vivo. The IC50 of 3j was 1.54± 0.41 µM lower than irinotecan with an IC50 of 13.86±0.80 µM in NCI-H460 cell, which was reduced by 8 fold. In NCI-H1975 cell, the IC50 of 3j was 1.87±0.23 µM lower than irinotecan (IC50±SD, 5.35±0.38 µM), dropped by 1.8 fold. Flow cytometry analysis revealed that 3j induced significant accumulation in a dose-dependent manner. After 24h of 3j (10 µM) treatment, the percentage of NCI-H460 cell in S-phase significantly increased (to 93.54 ± 4.4%) compared with control cells (31.67 ± 3.4%). Similarly, the percentage of NCI-H1975 cell in Sphase significantly increased (to 83.99 ± 2.4%) compared with control cells (34.45 ± 3.9%) after treatment with 10µM of 3j. Moreover, increased levels of cyclin A2, CDK2, and decreased levels of cyclin D, cyclin E further confirmed that cell cycle arrest was induced by 3j. Furthermore, molecular docking studies suggested that 3j interacted with Topo I-DNA and DNA-relaxation assay simultaneously confirmed that 3j suppressed the activity of Topo I. Research on the mechanism showed that 3j exhibited anti-tumour activity via activating the DNA damage response pathway and suppressing the repair pathway in NSCLC cells.

CONCLUSION

Novel camptothecin derivative 3j has been demonstrated as a promising antitumor agent and remains to be assessed in further studies.

C(sp2)-H Trifluoromethylation of enamides using TMSCF3: access to trifluoromethylated isoindolinones, isoquinolinones, 2-pyridinones and other heterocycles

A method for the direct C(sp2)-H trifluoromethylation of enamides, including biologically relevant isoindolinones, isoquinolinones and 2-pyridinones using TMSCF3 under oxidative conditions is presented. The protocol is convenient, operationally simple and exhibits high tolerance across a multitude of relevant handles and functional groups.

Fluorination methods in drug discovery

Fluorination reactions of medicinal and biologically-active compounds will be discussed. Late stage fluorination strategies of medicinal targets have recently attracted considerable attention on account of the influence that a fluorine atom can impart to targets of medicinal importance, such as modulation of lipophilicity, electronegativity, basicity and bioavailability, the latter as a consequence of membrane permeability. Therefore, the recourse to late-stage fluorine substitution on compounds with already known and relevant biological activity can provide the pharmaceutical industry with new leads with improved medicinal properties. The fluorination strategies will take into account different fluorinating reagents, either of nucleophilic or electrophilic, and of radical nature. Diverse families of organic compounds such as (hetero)aromatic rings, and aliphatic substrates (sp(3), sp(2), and sp carbon atoms) will be studied in late-stage fluorination reaction strategies.

Synthesis, antitumor activity, and mechanism of action of 6-acrylic phenethyl ester-2-pyranone derivatives

Based on the scaffolds of caffeic acid phenethyl ester (CAPE) as well as bioactive lactone-containing compounds, 6-acrylic phenethyl ester-2-pyranone derivatives were synthesized and evaluated against five tumor cell lines (HeLa, C6, MCF-7, A549, and HSC-2). Most of the new derivatives exhibited moderate to potent cytotoxic activity. Moreover, HeLa cell lines showed higher sensitivity to these compounds. In particular, compound showed potent cytotoxic activity (IC50 = 0.50-3.45 μM) against the five cell lines. Further investigation on the mechanism of action showed that induced apoptosis, arrested the cell cycle at G2/M phases in HeLa cells, and inhibited migration through disruption of the actin cytoskeleton. In addition, ADMET properties were also calculated in silico, and compound showed good ADMET properties with good absorption, low hepatotoxicity, and good solubility, and thus, could easily be bound to carrier proteins, without inhibition of CYP2D6. A structure-activity relationship (SAR) analysis indicated that compounds with ortho-substitution on the benzene ring exhibited obviously increased cytotoxic potency. This study indicated that compound is a promising compound as an antitumor agent.

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.

Explicit Ligand Hydration Shells Improve the Correlation between MM-PB/GBSA Binding Energies and Experimental Activities

Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) and Molecular Mechanics Generalized Born Surface Area (MM-GBSA) methods are widely used for drug design/discovery purposes. However, it is not clear if the correlation between predicted and experimental binding affinities can be improved by explicitly considering selected water molecules in the calculation of binding energies, since different and sometimes diverging opinions are found in the literature. In this work, we evaluated how variably populated hydration shells explicitly considered around the ligands may affect the correlation between MM-PB/GBSA computed binding energy and biological activities (IC50 and ΔGbind, depending on the available experimental data). Four different systems-namely, the DNA-topoisomerase complex, α-thrombin, penicillopepsin, and avidin-were considered and ligand hydration shells populated by 10-70 water molecules were systematically evaluated. We found that the consideration of a hydration shell populated by a number of water residues (Nwat) between 30 and 70 provided, in all of the considered examples, a positive effect on correlation between MM-PB/GBSA calculated binding affinities and experimental activities, with a negligible increment of computational cost.