Design, synthesis and biological evaluation of 2H-benzo[b][1,4] oxazine derivatives as hypoxia targeted compounds for cancer therapeutics

Design and Synthesis of Novel Antioxidant 2-Substituted-5,7,8-Trimethyl-1,4-Benzoxazine Hybrids: Effects on Young and Senescent Fibroblasts

The exponential growth of the aged population worldwide is followed by an increase in the prevalence of age-related disorders. Oxidative stress plays central role in damage accumulation during ageing and cell senescence. Thus, a major target of today's anti-ageing research has been focused on antioxidants counteracting senescence. In the current work, six novel 5,7,8-trimethyl-1,4-benzoxazine/catechol or resorcinol hybrids were synthesized connected through a methoxymethyl-1,2,3-triazolyl or a 1,2,3-triazoly linker. The compounds were evaluated for their antioxidant capacity in a cell-free system and for their ability to reduce intracellular ROS levels in human skin fibroblasts, both young (early-passage) and senescent. The most efficient compounds were further tested in these cells for their ability to induce the expression of the gene heme oxygenase-1 (ho-1), known to regulate redox homeostasis, and cellular glutathione (GSH) levels. Overall, the two catechol derivatives were found to be more potent than the resorcinol analogues. Furthermore, these two derivatives were shown to act coordinately as radical scavengers, ROS inhibitors, ho-1 gene expression inducers, and GSH enhancers. Interestingly, one of the two catechol derivatives was also found to enhance human skin fibroblast viability. The properties of the synthesized compounds support their potential use in cosmetic applications, especially in products targeting skin ageing.

Rational Design, Synthesis, and Anti-Proliferative Evaluation of Novel 4-Aryl-3,4-Dihydro-2H-1,4-Benzoxazines

A synthetic pathway to a novel 4-aryl-3,4-dihydro-2H-1,4-benzoxazine scaffold was developed and a series of compounds based on the scaffold were synthesised as potential anticancer agents. The 4-aryl-substituted compounds were prepared via Buchwald-Hartwig cross-coupling between substituted bromobenzenes and various 1,4-benzoxazines, which in turn were generated from a cascade hydrogenation and reductive amination one-pot reaction. These analogues exhibited moderate to good potency against various cancer cell lines. Structure-activity relationship analysis indicated that the inclusion of hydroxyl groups on ring A and ring B was beneficial to biological activity, while having a para-amino group on ring C significantly enhanced potency. Molecule 14f displayed the most potent anticancer activity (IC50 = 7.84-16.2 µM against PC-3, NHDF, MDA-MB-231, MIA PaCa-2, and U-87 MG cancer cell lines), indicating its potential as a lead compound for further structural optimisation. All the synthesised compounds were fully characterised with NMR, HMRS, and IR. The novel benzoxazine scaffold described in this study holds promise and deserves further in-depth studies.

Design and Synthesis of New Boron-Based Benzo[c][1,2,5]oxadiazoles and Benzo[c][1,2,5]thiadiazoles as Potential Hypoxia Inhibitors

Benzo[c][1,2,5]oxadiazoles and benzo[c][1,2,5]thiadiazoles are recognized to possess potent pharmacological activities including anticancer potential. In continuation of our research endeavors in the development of boron-based heterocycles as potential therapeutic agents, herein we report the design and synthesis of new series of boron-based benzo[c][1,2,5]oxadiazoles and benzo[c][1,2,5]thiadiazoles as anticancer agents targeting tumor hypoxia. A series of seventeen compounds were synthesized in two steps in an efficient manner via substitution reactions followed by subsequent hydrolysis of aryltrifluoroboronate salts into corresponding boronic acid derivatives in the presence of silica. This is the first example to develop boron-based hypoxia agents. The synthesized hybrids were characterized by suitable spectroscopic techniques. The biological studies are currently underway.

Synthetic Methods and Pharmacological Potential of Different Oxazine Analogs

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Oxazine analog is a vital class of heterocyclic compounds and has attracted synthetic interest owing to their wide range of biological activities. Oxazine analogs are valuable in medicinal organic chemistry and exhibit different varieties of biological activities such as antimicrobial, anticancer, antimalarial, antitubercular, sedative, anticonvulsant, analgesic, anti-inflammatory, antipyretic, etc. Oxazine can be derived from benzene by appropriate substitution of carbon atoms of the ring by nitrogen and oxygen atoms. Nowadays, the development of drug resistance is a key problem, and to defeat this problem, it is crucial to synthesize novel compounds. So, novel oxazine analogs may play a crucial role to overcome these problems. Oxazine analogs are prepared by reaction of chalcone derivatives with thiourea in the presence of alcohol and sodium hydroxide. The present aims of this review are to give an outline of some different synthetic methods and different types of biological activities of oxazine analogs. We hope that this review will be motivating for researchers concerned with oxazine analogs.

Polymer-Supported Syntheses of Heterocycles Bearing Oxazine and Thiazine Scaffolds

In this review, we summarize synthetic approaches to preparing single or fused oxazine and thiazine derivatives using solid-phase synthesis (SPS). The literature survey revealed that diverse compounds bearing variously functionalized 1,2-oxazine, 1,3-oxazine, or 1,4-oxazine scaffolds and the corresponding thiazines are accessible by SPS. The latest contributions involving the stereoselective polymer-supported syntheses of morpholines indicate that the field is continuing to expand.

Cobalt Ion Promoted Redox Cascade: A Route to Spiro Oxazine-Oxazepine Derivatives and a Dinuclear Cobalt(III) Complex of an N-(1,4-Naphthoquinone)-o-aminophenol Derivative

The study discloses that the redox activity of N-(1,4-naphthoquinone)-o-aminophenol derivatives (L^RH₂) containing a (phenol)-NH-(1,4-naphthoquinone) fragment is notably different from that of a (phenol)-NH-(phenol) precursor. The former is a platform for a redox cascade. L^RH₂ is redox noninnocent and exists in Cat-N-(1,4-naphthoquinone)(2-) (L^R 2-) and SQ-N-(1,4-naphthoquinone) (L^R •-) states in the complexes. Reactions of L^RH₂ with cobalt(II) salts in MeOH in air promote a cascade affording spiro oxazine-oxazepine derivatives (^OXL^R) in good yields, when R = H, Me, ^tBu. Spiro oxazine-oxazepine derivatives are bioactive, and such a molecule has so far not been isolated by a schematic route. In this context this cascade is significant. Dimerization of L^RH₂ → ^OXL^R in MeOH is a (6H⁺ + 6e) oxidation reaction and is composed of formations of four covalent bonds and 6-exo-trig and 7-endo-trig cyclization based on C-O coupling reactions, where MeOH is the source of a proton and the ester function. It was established that the active cascade precursor is [(L^Me •-)Co^IIICl₂] (A). Notably, formation of a spiro derivative was not detected in CH₃CN and the reaction ends up furnishing A. The route of the reaction is tunable by R, when R = NO₂, it is a (2e + 4H⁺) oxidation reaction affording a dinuclear L^R 2- complex of cobalt(III) of the type [(L^NO2 2-)₂Co^III₂(OMe)₂(H₂O)₂] (1) in good yields. No cascade occurs with zinc(II) ion even in MeOH and produces a L^Me •- complex of type [(L^Me •-)Zn^IICl₂] (2). The intermediate A and 2 exhibit strong EPR signals at g = 2.008 and 1.999, confrming the existence of L^Me •- coordinated to low-spin cobalt(III) and zinc(II) ions. The intermediates of L^RH₂ → ^OXL^R conversion were analyzed by ESI mass spectrometry. The molecular geometries of ^OXL^R and 1 were confirmed by X-ray crystallography, and the spectral features were elucidated by TD DFT calculations.

Molecular Engineering of Tetracyclic 2,3-Dihydro-1H-benzo[2,3]-benzofuro[4,5-e][1,3]oxazine Derivatives: Evaluation for Potential Anticancer Agents

Water-mediated one-pot Mannich type condensation of dibenzo[b,d]furan-2-ol with different amines resulted in a large library of novel 2,3-dihydro-1H-benzo[2,3]benzofuro[4,5-e][1,3]oxazine derivatives in moderate to excellent yields. The ortho-aminomethylation of the dibenzofuranols proceeded smoothly in the presence of various aromatic/aliphatic amines and paraformaldehyde, followed by cyclization. All the newly synthesized tetracyclic 2,3-dihydro-1H-benzo[2,3]benzofuro[4,5-e][1,3]oxazine derivatives were chemically characterized and screened for their cytotoxicity activity by cell viability assay (MTT test) against three human cancer cell lines and antibacterial activity by determining the minimum inhibitory concentration (MIC) against four bacterial strains. Among all the derivatives, MCV-24 showed promising anticancer activity by inhibiting the cell proliferation of an ovarian cancer cell line (SKOV3) with an IC₅₀ value at 7.5 µM, whereas MCV-24 to MCV-30 derivatives showed moderate activity against a lung cancer cell line (A549) with an IC₅₀ value ranging from 11 to 15.9 µM. Besides MCV-29, -30, and -31 also exhibited broad-spectrum antibacterial activity. Among all new compounds, MCV-24-30 showed promising anticancer and MCV-29-31 antibacterial activity.

Skeletally Diverse Synthesis of Innovative [2,1-c]-1,4-Oxazepine and [1,4]-Quinoxaline Systems

An efficient, innovative synthesis of [2,1-c]-1, 4-oxazepine and [1,4]-quinoxaline heterocycles along with the embodied pyrimido-pyrrolo motifs was established. Initially, the pyrrole ring was installed using microwave irradiation through an intramolecular base-catalyzed cyclization between acetyl bromomethyl pyrimidine dione and o-amino phenyl methanol or o-phenylenediamine methyl benzoates. Furthermore, oxazepine, and quinoxaline scaffolds were constructed by an acid-catalyzed condensation with a variety of aldehydes by an unconventional Pictet-Spengler reaction strategy. An important aspect of this work is to build novel heterocyclic ring systems with potential medicinal interest.

Chemical modulation of chaperone-mediated autophagy by retinoic acid derivatives

Chaperone-mediated autophagy (CMA) contributes to cellular quality control and the cellular response to stress through the selective degradation of cytosolic proteins in lysosomes. Decrease in CMA activity occurs in aging and in age-related disorders (for example, neurodegenerative diseases and diabetes). Although prevention of this age-dependent decline through genetic manipulation in mouse has proven beneficial, chemical modulation of CMA is not currently possible, due in part to the lack of information on the signaling mechanisms that modulate this pathway. In this work, we report that signaling through the retinoic acid receptor alpha (RARα) inhibits CMA and apply structure-based chemical design to develop synthetic derivatives of all-trans-retinoic acid (ATRA) to specifically neutralize this inhibitory effect. We demonstrate that chemical enhancement of CMA protects cells from oxidative stress and from proteotoxicity, supporting a potential therapeutic opportunity when reduced CMA contributes to cellular dysfunction and disease.

Novel retinoic acid receptor alpha agonists for treatment of kidney disease

Development of pharmacologic agents that protect podocytes from injury is a critical strategy for the treatment of kidney glomerular diseases. Retinoic acid reduces proteinuria and glomerulosclerosis in multiple animal models of kidney diseases. However, clinical studies are limited because of significant side effects of retinoic acid. Animal studies suggest that all trans retinoic acid (ATRA) attenuates proteinuria by protecting podocytes from injury. The physiological actions of ATRA are mediated by binding to all three isoforms of the nuclear retinoic acid receptors (RARs): RARα, RARβ, and RARγ. We have previously shown that ATRA exerts its renal protective effects mainly through the agonism of RARα. Here, we designed and synthesized a novel boron-containing derivative of the RARα-specific agonist Am580. This new derivative, BD4, binds to RARα receptor specifically and is predicted to have less toxicity based on its structure. We confirmed experimentally that BD4 binds to RARα with a higher affinity and exhibits less cellular toxicity than Am580 and ATRA. BD4 induces the expression of podocyte differentiation markers (synaptopodin, nephrin, and WT-1) in cultured podocytes. Finally, we confirmed that BD4 reduces proteinuria and improves kidney injury in HIV-1 transgenic mice, a model for HIV-associated nephropathy (HIVAN). Mice treated with BD4 did not develop any obvious toxicity or side effect. Our data suggest that BD4 is a novel RARα agonist, which could be used as a potential therapy for patients with kidney disease such as HIVAN.

Design, synthesis and biological study of pinacolyl boronate-substituted stilbenes as novel lipogenic inhibitors

A pilot library of novel 4,4,5,5-tetramethyl-2-(4-substitutedstyrylphenyl)-1,3,2 dioxaborolane derivatives has been synthesized. 4-(4,4,5,5-Tetramethyl-1,3,2-dioxaboratophenyl)-methyl triphenylphosphonium bromide 3 was treated with various aldehydes in the presence of 3 equiv of (t)BuONa in DMF, and stirred at room temperature for 4-6h to yield the corresponding boron-containing stilbene derivatives in 71-94% yields. Several of them, including BF102 and BF175, have the lipogenesis inhibitory effect by suppressing lipogenic gene expression in mammalian hepatocytes. Further, BF102 also inhibits cholesterol biosynthesis by suppressing HMG-CoA reductase gene expression in hepatocytes. Interestingly, our preliminary in vivo data suggests that BF102 has no significant toxicity in mice at the highest possible dose we can administered. Thus, BF102 is a potential lead for the next generation of lipid-lowering drugs.

Synthesis and antiproliferative activity of oxazinocarbazole and N,N-bis(carbazolylmethyl)amine derivatives

The synthesis, structure elucidation and antitumoral activity of novel heterocyclic compounds containing a carbazole nucleus are reported. Oxazinocarbazoles were synthesized by application of the Mannich reaction to the corresponding hydroxylated derivatives leading to 41 new molecules. Their cytotoxic activity was evaluated against various human tumor cell lines including three leukemic cell lines: CEM and Jurkat (type T), Raji (type B); breast cancer cell line (MCF-7); colorectal cancer cell line (Caco-2). A primary screening at 100 microM allowed the selection of the 10 most active compounds, which showed an antiproliferative activity on all the cell lines. A dose-effect study between 12.5 and 100 microM sorted two compounds with a significant activity: 5t and 7e against leukemic cell lines CEM, Jurkat and Raji with IC50 values around 12 microM.