Dependence of the anticancer activity of 1,3‐oxazole derivatives on the donor/acceptor nature of his substitues

Recyclization of 5-Amino- oxazoles as a Route to new Functionalized Heterocycles (Developments of V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the NAS of Ukraine)

The recyclizations of 5-amino- and 5-hydrazine-1,3-oxazoles mainly with electron-withdrawing group in 4th position are considered. The chemical behavior of these heterocycles is due to the presence of two hidden amide fragments; therefore, the recyclization processes include a stage of nucleophile attack on 2nd or 5th position of the oxazole cycle. When the nitrile group is present in 4th position, it is often involved in the recyclization forming α-aminoazoles. 5-Amino/hydrazine-1,3-oxazoles undergo recyclization both in nucleophilic (amines, hydrazine, thionating agents) and electrophilic medium ((trifluoro)acetic acid, other acylating agents). The numerous types of functionalized heterocycles can be easily obtained with the usage of these recyclizations, such as the derivatives of 3-amino-6,7-dihydro-5H-pyrrolo[1,2-a]imidazole, imidazolidine-2,4-dione, 1H-pyrazole-3,4,5-triamine, 5,6-diamino-2,3-diphenylpyrimidin-4(3H)-one, 2-(2-R-7-oxo-5-(trifluoromethyl)oxazolo[5,4-d]pyrimidin-6(7H)-yl)acetic acid, 2-R-4-(5-R'-1,3,4-oxadiazol-2-yl)oxazol-5-amine, (amino(5-amino-1,3,4-thiadiazol-2-yl)methyl)phosphonate.

New Benzimidazoles Targeting Breast Cancer: Synthesis, Pin1 Inhibition, 2D NMR Binding, and Computational Studies

Benzimidazole derivatives are known to be key players in the development of novel anticancer agents. Herein, we aimed to synthesize novel derivatives to target breast cancer. A new series of benzimidazole derivatives conjugated with either six- and five-membered heterocyclic ring or pyrazanobenzimidazoles and pyridobenzimidazole linkers were synthesized yielding compounds 5–8 and 10–14, respectively. Structure elucidation of the newly synthesized compounds was achieved through microanalytical analyses and different spectroscopic techniques (¹H, ¹³C-APT and ¹H–¹H COSY and IR) in addition to mass spectrometry. A biological study for the newly synthesized compounds was performed against breast cancer cell lines (MCF-7), and the most active compounds were further subjected to normal Human lung fibroblast (WI38) which indicates their safety. It was found that most of them exhibit high cytotoxic activity against breast cancer (MCF-7) and low cytotoxic activity against normal (WI38) cell lines. Compounds 5, 8, and 12, which possess the highest anti-breast cancer activity against the MCF-7 cell line, were selected for Pin1 inhibition assay using tannic acid as a reference drug control. Compound 8 was examined for its effect on cell cycle progression and its ability to apoptosis induction. Mechanistic evaluation of apoptosis induction was demonstrated by triggering intrinsic apoptotic pathways via inducing ROS accumulation, increasing Bax, decreasing Bcl-2, and activation of caspases 6, 7, and 9. Binding to 15N-labeled Pin1 enzyme was performed using state-of-the-art ¹⁵N–¹H HSQC NMR experiments to describe targeting breast cancer on a molecular level. In conclusion, the NMR results demonstrated chemical shift perturbation (peak shifting or peak disappearance) upon adding compound 12 indicating potential binding. Molecular docking using ‘Molecular Operating Environment’ software was extremely useful to elucidate the binding mode of active derivatives via hydrogen bonding.

In silico and in vitro Estimation of Structure and Biological Affinity of 1,3- Oxazoles: Fragment-to-fragment Approach

Background:

The fragment-to-fragment approach for the estimation of the biological af-finity of the pharmacophores with biologically active molecules has been proposed. It is the next step in the elaboration of molecular docking and using the quantum-chemical methods for the complex modeling of pharmacophores with biomolecule fragments.

Methods:

The parameter 0 was used to estimate the contribution of -electron interactions in bio-logical affinity. It is directly related to the position of the frontier levels and reflects the donor-accep-tor properties of the pharmacophores and stabilization energy of the [Pharm꞉BioM] complex.

Results:

By using quantum-chemical calculations, it was found that the stacking interaction of oxa-zoles with phenylalanine is 7-11 kcal/mol, while the energy of hydrogen bonding of oxazoles with the amino group of lysine is 5-9 kcal/mol. The fragment-to-fragment approach can be applied for the investigation of the dependence of biological affinity on the electronic structure of pharmacophores.

Conclusion:

The founded quantum-chemical regularities are confirmed with the structure-activity relationships of substituted oxazoles.

Recent Developments in Oxazole Derivatives as Anticancer Agents: Review on Synthetic Strategies, Mechanism of Action and SAR studies

BACKGROUND

Cancer is the world's third deadliest disease. Despite the availability of numerous treatments, researchers are focusing on the development of new drugs lacking resistance and toxicity issues. Many newly synthesized drugs fail to reach clinical trials due to poor pharmacokinetic properties. Therefore, there is an imperative requisite to expand novel anticancer agents with in vivo efficacy.

OBJECTIVE

This review emphasizes synthetic methods, contemporary strategies used for the inclusion of oxazole moiety, mechanistic targets along with comprehensive structure-activity relationship studies to provide perspective into the rational design of highly efficient oxazole-based anticancer drugs.

METHODS

Literature related to oxazole derivatives engaged in cancer research is reviewed. This article gives a detailed account of synthetic strategies, targets of oxazole in cancer, including STAT3, Microtubules, G-quadruplex, DNA topoisomerases, DNA damage, Protein kinases, miscellaneous targets, in vitro studies, and some SAR studies.

RESULTS

Oxazole derivatives possess potent anticancer activity by inhibiting novel targets such as STAT3 and G-quadruplex. Oxazoles also inhibit tubulin protein to induce apoptosis in cancer cells. Some other targets such as DNA topoisomerase enzyme, protein kinases, and miscellaneous targets including Cdc25, mitochondrial enzymes, HDAC, LSD1, HPV E2 TAD, NQO1, Aromatase, BCl-6, Estrogen receptor, GRP-78, and Keap-Nrf2 pathway are inhibited by oxazole derivatives Many derivatives showed excellent potencies on various cancer cell lines with IC50 values in nanomolar concentrations.

CONCLUSION

Oxazole is a five-membered heterocycle, with oxygen and nitrogen at 1 and 3 positions respectively. It is often combined with other pharmacophores in the expansion of novel anticancer drugs. In summary, oxazole is a promising entity to develop new anticancer drugs.

Anticancer activity of benzoxazole derivative (2015 onwards): a review

Background

According to the report published recently by the World Health Organization, the number of cancer cases in the world will increase to 22 million by 2030. So the anticancer drug research and development is taking place in the direction where the new entities are developed which are low in toxicity and are with improved activity. Benzoxazole and its derivative represent a very important class of heterocyclic compounds, which have a diverse therapeutic area. Recently, many active compounds synthesized are very effective; natural products isolated with benzoxazole moiety have also shown to be potent towards cancer.

Main text

In the last few years, many research groups have designed and developed many novel compounds with benzoxazole as their backbone and checked their anticancer activity. In the review article, the recent developments (mostly after 2015) made in the direction of design and synthesis of new scaffolds with very potent anticancer activity are briefly described. The effect of various heterocycles attached to the benzoxazole and their effect on the anticancer activity are thoroughly studied and recorded in the review.

Conclusion

These compiled data in the article will surely update the scientific community with the recent development in this area and will provide direction for further research in this area.