The new 5- or 6-azapyrimidine and cyanuric acid derivatives of l-ascorbic acid bearing the free C-5 hydroxy or C-4 amino group at the ethylenic spacer: CD-spectral absolute configuration determination and biological activity evaluations

1,3,5-Triazine Analogs: A Potent Anticancer Scaffold

Background:

This review presents the exhaustive exploration of 1,3,5-triazine scaffold for development of analogs of anticancer drugs, over the last century. In the recent years, striazine moiety has been one of the most studied moiety, showing broad-spectrum pharmacological activities such as antibacterial, antifungal, analgesic, anti-HIV, antileishmanial, antitrypanosomal, antimalarial and antiviral. Nowadays, many boffins are have become interested in novel synthesis of s-triazine derivatives because of low cost and ease of availability.

Methods:

This scaffold has been extensively investigated mainly in the past decade. Many products have been synthesized from different starting materials and these synthetic products possess anticancer potential against various cell lines.

Results:

Many 1,3,5-triazine analogs exhibited significant anticancer activity in various models and cell lines exhibiting different mechanisms. Some analogs have also shown good pharmacokinetic parameters with less IC50 values.

Conclusion:

Various 1,3,5-triazine analogs have shown potent activities and may be regarded as clinical candidates for future anticancer formulations. This review may be helpful to those researchers seeking required information with regard to the drug design and medicinal properties of 1,3,5-triazine derivatives for selected targets. This review may also offer help to find and improve clinically viable anticancer molecules.

Therapeutic Perspective of Vitamin C and Its Derivatives

l-Ascorbic acid (ASA), vitamin C, is a ubiquitous carbohydrate-like compound that has an essential role in a number of cellular processes, such as collagen synthesis, cellular oxidation, and various hydroxylation reactions. ASA is a biomolecule of critical importance for protection of cellular components against oxidative damage caused by toxic free radicals and other reactive oxygen species (ROS) that are involved in the development of various types of chronic diseases. Vitamin C has a switchover role from being an antioxidant in physiological conditions to a prooxidant under pathologic conditions. Moreover, some l-ascorbic acid derivatives exhibit strong and selective antitumor and antiviral activity. This review emphasizes the advances on diverse and potent biological profiles of l-ascorbic acid and its derivatives, and their perspective in the development of new bioactive chemical entities in the future. The work is primarily addressed at antioxidant, anticancer, and antiviral potencies of l-ascorbic acid and compounds containing its butenolide structural motif.

Initial biological evaluations of 18F-KS1, a novel ascorbate derivative to image oxidative stress in cancer

Background

Reactive oxygen species (ROS)-induced oxidative stress damages many cellular components such as fatty acids, DNA, and proteins. This damage is implicated in many disease pathologies including cancer and neurodegenerative and cardiovascular diseases. Antioxidants like ascorbate (vitamin C, ascorbic acid) have been shown to protect against the deleterious effects of oxidative stress in patients with cancer. In contrast, other data indicate potential tumor-promoting activity of antioxidants, demonstrating a potential temporal benefit of ROS. However, quantifying real-time tumor ROS is currently not feasible, since there is no way to directly probe global tumor ROS. In order to study this ROS-induced damage and design novel therapeutics to prevent its sequelae, the quantitative nature of positron emission tomography (PET) can be harnessed to measure in vivo concentrations of ROS. Therefore, our goal is to develop a novel translational ascorbate-based probe to image ROS in cancer in vivo using noninvasive PET imaging of tumor tissue. The real-time evaluations of ROS state can prove critical in developing new therapies and stratifying patients to therapies that are affected by tumor ROS.

Methods

We designed, synthesized, and characterized a novel ascorbate derivative (E)-5-(2-chloroethylidene)-3-((4-(2-fluoroethoxy)benzyl)oxy)-4-hydroxyfuran-2(5H)-one (KS1). We used KS1 in an in vitro ROS MitoSOX-based assay in two different head and neck squamous cancer cells (HNSCC) that express different ROS levels, with ascorbate as reference standard. We radiolabeled ¹⁸F-KS1 following ¹⁸F-based nucleophilic substitution reactions and determined in vitro reactivity and specificity of ¹⁸F-KS1 in HNSCC and prostate cancer (PCa) cells. MicroPET imaging and standard biodistribution studies of ¹⁸F-KS1 were performed in mice bearing PCa cells. To further demonstrate specificity, we performed microPET blocking experiments using nonradioactive KS1 as a blocker.

Results

KS1 was synthesized and characterized using ¹H NMR spectra. MitoSOX assay demonstrated good correlations between increasing concentrations of KS1 and ascorbate and increased reactivity in SCC-61 cells (with high ROS levels) versus rSCC-61cells (with low ROS levels). ¹⁸F-KS1 was radiolabeled with high radiochemical purity (> 94%) and specific activity (~ 100 GBq/μmol) at end of synthesis (EOS). Cell uptake of ¹⁸F-KS1 was high in both types of cancer cells, and the uptake was significantly blocked by nonradioactive KS1, and the ROS blocker, superoxide dismutase (SOD) demonstrating specificity. Furthermore, ¹⁸F-KS1 uptake was increased in PCa cells under hypoxic conditions, which have been shown to generate high ROS. Initial in vivo tumor uptake studies in PCa tumor-bearing mice demonstrated that ¹⁸F-KS1 specifically bound to tumor, which was significantly blocked (threefold) by pre-injecting unlabeled KS1. Furthermore, biodistribution studies in the same tumor-bearing mice showed high tumor to muscle (target to nontarget) ratios.

Conclusion

This work demonstrates the strong preliminary support of ¹⁸F-KS1, both in vitro and in vivo for imaging ROS in cancer. If successful, this work will provide a new paradigm to directly probe real-time oxidative stress levels in vivo. Our work could enhance precision medicine approaches to treat cancer, as well as neurodegenerative and cardiovascular diseases affected by ROS.

Electronic supplementary material

The online version of this article (10.1186/s13550-019-0513-x) contains supplementary material, which is available to authorized users.

Cascade reactions of nitrogen-substituted isocyanates: a new tool in heterocyclic chemistry

In contrast to normal C-substituted isocyanates, nitrogen-substituted isocyanates (N-isocyanates) are rare. Their high reactivity and amphoteric/ambident nature has prevented the scientific community from exploiting their synthetic potential. Recently, we have developed an in situ formation approach using a reversible equilibrium, which allows controlled generation and reactivity of N-isocyanates and prevents the dimerization that is typically observed with these intermediates. This blocked (masked) N-isocyanate approach enables the use of various N-isocyanate precursors to assemble heterocycles possessing the N-N-C[double bond, length as m-dash]O motif, which is often found in agrochemicals and pharmaceuticals. Cascade reactions for the rapid assembly of several valuable 5- and 6-membered heterocycles are reported, including amino-hydantoins, acyl-pyrazoles, acyl-phthalazinones and azauracils. Over 100 different compounds were synthesized using amino-, imino- and amido-substituted N-isocyanates, demonstrating their potential as powerful intermediates in heterocyclic synthesis. Their reactivity also enables access to unprecedented bicyclic derivatives and to substitution patterns of azauracils that are difficult to access using known methods, illustrating that controlled reactivity of N-isocyanates provides new disconnections, and a new tool to assemble complex N-N-C[double bond, length as m-dash]O containing motifs.

Polymeric (anion-π)n interactions in crystals of 2-(2,4,6-trioxo-[1,3,5]triazinan-1-yl)ethylammonium iodide

2-(2,4,6-Trioxo-[1,3,5]triazinan-1-yl)ethyammonium halides

Novel halogenated 3-deazapurine, 7-deazapurine and alkylated 9-deazapurine derivatives of L-ascorbic or imino-L-ascorbic acid: Synthesis, antitumour and antiviral activity evaluations

Keeping the potential synergy of biological activity of synthetic anomalous derivatives of deazapurines and l-ascorbic acid (l-AA) in mind, we have synthesized new 3-, 7- and 9-deazapurine derivatives of l-ascorbic (1–4, 8–10, 13–15) and imino-l-ascorbic acid (5–7, 11, 12, 16–19). These novel compounds were evaluated for their cytostatic and antiviral activity in vitro against a panel of human malignant tumour cell lines and normal murine fibroblasts (3T3). Among all evaluated compounds, the 9-deazapurine derivative of l-AA (13) exerted the most potent inhibitory activity on the growth of CEM/0 cells (IC₅₀ = 4.1 ± 1.8 μM) and strong antiproliferative effect against L1210/0 (IC₅₀ = 4.7 ± 0.1 μM) while the 9-deazahypoxanthine derivative of l-AA (15) showed the best effect against HeLa cells (IC₅₀ = 5.6 ± 1.3 μM) and prominent effect on L1210/0 (IC₅₀ = 4.5 ± 0.5 μM). Furthermore, the 9-deazapurine derivative disubstituted with two imino-l-AA moieties (18) showed the best activity against L1210/0 tumour cells (IC₅₀ = 4.4 ± 0.3 μM) and the most pronounced antiproliferative effects against MiaPaCa-2 cells (IC₅₀ = 5.7 ± 0.2 μM). All these compounds showed selective cytostatic effect on tumour cell lines in comparison with embryonal murine fibroblasts (3T3). When evaluating their antiviral activity, the 3-deazapurine derivative of l-AA (3) exhibited the highest activity against both laboratory-adapted strains of human cytomegalovirus (HCMV) (AD-169 and Davis) with EC₅₀ values comparable to those of the well-known anti-HCMV drug ganciclovir and without cytotoxic effects on normal human embryonal lung (HEL) cells.

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Deazapurine derivatives of l-ascorbic and imino-l-ascorbic acid were synthesized.

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Compound 13 exerted strong activity on the growth of CEM/0 and L1210/0 cells.

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Compound 15 showed the best cytostatic effect against HeLa cells.

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Compound 18 showed the best cytostatic activity against L1210/0 and MiaPaCa-2.

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Compound 3 exhibited highest effect against HCMV comparable to ganciclovir.

Molecular structure and vibrational spectra of 2-Ethoxymethyl-6-ethyl-2,3,4,5-tetrahydro-1,2,4-triazine-3,5-dione, a potential chemotherapeutic agent, by density functional methods

In this work, the vibrational spectral analysis was carried out using FT-IR and FT-Raman spectroscopy for 2-Ethoxymethyl-6-ethyl-2,3,4,5-tetrahydro-1,2,4-triazine-3,5-dione, which is a potential chemotherapeutic agent derivative. Theoretical calculations were performed by density functional methods. The complete vibrational assignments of the wavenumbers were made on the basis of potential energy distribution. The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with the observed spectra. The frontier orbital energy gap and related properties of the molecule illustrates the high reactivity of the title compound. The first order hyperpolarizability, dipole moment and polarizability are also calculated. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis. Molecular electrostatic potential map is also constructed. The calculated geometrical parameters are in agreement with the XRD results.