Review on Synthesis and Medicinal Application of Dihydropyrano[3,2-b]Pyrans and Spiro-Pyrano[3,2-b]Pyrans by Employing the Reactivity of 5-Hydroxy-2-(Hydroxymethyl)-4H-Pyran-4-One

In silico evaluation of potential breast cancer receptor antagonists from GC-MS and HPLC identified compounds in Pleurotus ostreatus extracts

Introduction: Pharmacotherapeutic targets for breast cancer include the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor (EGFR). Inhibitors of these receptors could be interesting therapeutic candidates for the treatment and management of breast cancer (BC). Aim: This study used GC-MS and HPLC to identify bioactive compounds in Pleurotus ostreatus (P. ostreatus) extracts and applied in silico methods to identify potent EGFR, ER, and PR inhibitors from the compounds as potential drug candidates. Method: GC-MS and HPLC were used to identify bioactive chemicals in P. ostreatus extracts of aqueous (PO-A), methanol (PO-M), ethanol (PO-E), chloroform (PO-C), and n-hexane (PO-H). The ER, PR, and EGFR model optimization and molecular docking of compounds/control inhibitors in the binding pocket were simulated using AutoDock Vina in PyRx. The drug-likeness, pharmacokinetic, and pharmacodynamic features of prospective docking leads were all anticipated. Result: The results indicated the existence of 29 compounds in PO-A, 36 compounds in PO-M and PO-E, 42 compounds in PO-C, and 22 compounds in PO-H extracts. With ER, only o-tolylamino-acetic acid (4-nitro-benzylidene)-hydrazide (-7.5 kcal mol-1) from the ethanolic extract could bind to the receptor. PR and EGFR, on the other hand, identified several compounds with higher binding affinities than the control. Ergotaman-3',6',18-trione (-8.1 kcal mol-1), 5,10-diethoxy-2,3,7,8-tetrahydro-1H,6H-dipyrrolo[1,2-a:1',2'-d]pyrazine (-7.8 kcal mol-1) from the aqueous extract; o-tolylamino-acetic acid (4-nitro-benzylidene)-hydrazide (-8.4 kcal mol-1) from the ethanolic extract had better binding affinity compared to progesterone (-7.7 kcal mol-1). Likewise, ergotaman-3',6',18-trione (-9.7 kcal mol-1) from the aqueous extract and phenol, 2,4-bis(1,1-dimethyl ethyl) (-8.2 kcal mol-1) from the chloroform extract had better binding affinities compared to the control, gefitinib (-7.9 kcal mol-1) with regards to EGFR. None of the PO-H or PO-M extracts outperformed the control for any of the proteins. Phenols and flavonoids such as quercetin, luteolin, rutin, chrysin, apigenin, ellagic acid, and naringenin had better binding affinity to PR and EGFR compared to their control. Conclusion: The identified compounds in the class of phenols and flavonoids were better lead molecules due to their ability to strongly bind to the proteins' receptors. These compounds showed promising drug-like properties; they could be safe and new leads for creating anticancer medicines.

Update on thiopyran-fused heterocycle synthesis (2013-2024)

Thiopyrans and their fused derivatives have significant synthetic relevance owing to their biological importance and occurrence in natural products. The current article provides an overview of synthetic strategies employed for the construction of thiopyran-fused heterocycles. In particular, this article discusses synthetic methods for the fusion of thiopyran with heterocycles such as indole, quinoline, pyrimidine, pyridine, thiophene, chromene, oxazole, pyrazole, pyran and furan and covers the literature from 2013 to 2024. The most common precursors for thiopyrano[2,3-b]indoles, thiopyranoquinolines and thiopyranothiazoles are indoline-2-thione, 2-mercaptoquinoline-3-carbaldehyde and thiazolidinone, respectively, and various reactions involving these are described in detail here. Asymmetric syntheses of thiopyranoindoles achieved using chiral catalysts based on thiourea, proline and metal complexes are also included. The biological activity associated with some compounds is also discussed.

5-Oxo-dihydropyranopyran derivatives as anti-proliferative agents; synthesis, biological evaluation, molecular docking, MD simulation, DFT, and in-silico pharmacokinetic studies

A series of ethyl 2-amino-7-methyl-5-oxo-4-phenyl-4,5-dihydropyrano[4,3-b]pyran-3-carboxylate derivatives (4a-j) bearing different substitutions on the C4-phenyl ring was synthesized. The anti-proliferative activity of all the synthesized compounds was assessed against two human cancer-cell lines, including SW-480 and MCF-7, by using MTT method. Derivatives 4g, 4i, and 4j, possessing 4-NO2, 4-Cl, and 3,4,5-(OCH3)3 substitutions, were found to be the most potent compounds against both cell lines. The obtained IC50 values for 4g, 4i, and 4j were 34.6, 35.9, and 38.6 μM against SW-480 cells and 42.6, 34.2, and 26.6 μM against MCF-7 cells, respectively. Evaluation of the free radical scavenging potential of the compounds against DPPH radicals showed the highest result for compound 4j with an EC50 value of 580 μM. Molecular docking studies revealed the compounds were well accommodated within the binding site of cyclin-dependent kinase-2 (CDK2) with binding energies comparable to those of DTQ (the co-crystallized inhibitor) and BMS-265246 (a well-known CDK2 inhibitor). Molecular dynamics simulation studies confirmed the interactions and stability of the 4g-CDK2 complex. All derivatives, except 4g, were predicted to comply with the drug-likeness rules. Compound 4j may be proposed as an anti-cancer lead candidate for further studies due to the promising findings from in-silico pharmacokinetic studies, such as high GI absorption, not being a P-gp substrate, and being a P-gp inhibitor. Density functional theory (DFT) analysis was performed at the B3LYP/6-311++G (d,p) level of theory to examine the reactivity or stability descriptors of 4d, 4g, 4i, and 4j derivatives. The highest value of energy gap between HOMO and LUMO and thermochemical parameters were obtained for 4i and 4j.

Efficient synthesis of new indenopyridotriazine [4.3.3]propellanes and spiroindenopyridotriazine-4H-pyran derivatives

The pyrido[1,2,4]triazines as substrates, generated from 1,6-diaminopyridinone derivatives and ninhydrin, were reacted with malononitrile and CH-acids to afford a new library spiro[indeno[1,2-e]pyrido[1,2-b][1,2,4]triazine-7,5'-pyran]-1,3,6'-tricarbonitrile in ethanol at reflux condition in excellent yield. Also, novel indenopyridotriazine [4.3.3]propellanes were synthesized via the reaction of pyrido[1,2,4]triazine and N-methyl-1-(methylthio)-2-nitroethenamine (NMSM) by using of HOAc in ethanol. The important aspects of this protocol are the abundance of starting materials, mild conditions, structural diversity of products, excellent yields and easy isolation of products with no chromatographic technique.

A ratiometric fluorescent probe based on spiropyran in situ switching for tracking dynamic changes of lysosomal autophagy and anticounterfeiting

Autophagy is the controlled breakdown of cellular components that dysfunctional or nonessential, and the decomposition products are further recycled and synthesized for the normal physiological activities of cells. Lysosomal autophagy has been implicated in cancer, neurological disorders, Parkinson's disease, etc. Therefore, it is necessary to develop a fluorescent probe that can clearly describe the process of lysosomal autophagy. However, there are currently limited fluorescent probes for ratiometric monitoring of the autophagic process in dual channels. To solve this problem, a fluorescent probe based on spiropyran with lysosomal targeting and pH response for ratiometric monitoring the autophagy process of lysosomes were designed. The sensitive response of the probe to pH in vitro was verified by UV and fluorescence spectrum tests. Meanwhile, the probe demonstrated the ability to monitor the intracellular pH fluctuations. In addition, the application of Lyso-SD in the field of anti-counterfeiting has been proposed based on the obvious photoluminescence ability of Lyso-SD under UV irradiation.

Stereoselective synthesis of CF3-containing spirocyclic-oxindoles using N-2,2,2-trifluoroethylisatin ketimines: an update

The introduction of fluorine-containing groups into organic molecules either changes or improves the characteristics of the target compounds. On the other hand, spirocyclic-oxindoles featuring C-3 functionalized sp3-hybridized carbon atoms of three-dimensional orthogonally shaped molecules were well recognized in the core structure of varied natural products and synthetic pharmaceutical targets. Consequently, the construction of spirooxindoles by an elegant synthetic approach with efficient stereocontrol has received tremendous interest over the past decades. In this context of the synergic combination of the features associated with fluorine-containing compounds and the synthetic and medicinal efficiency associated with spirooxindoles, the stereodivergent installation of CF3 groups embedded with spirooxindoles is of increasing academic and scientific interest. This mini-review article is dedicated to demonstrating a critical overview of the recent stereoselective synthesis of spirocyclic-oxindoles featuring trifluoromethyl groups by employing the reactivity of N-2,2,2-trifluoroethylisatin ketimines as an efficient and easily prepared synthon, and covers the literature reports from 2020 to date. Besides exploring the advancements accomplished in this area, we also investigate the limitations associated with reaction discovery, mechanistic rationalization, and future applications.

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

Heterocycles of synthetic and natural origin are a well-established class of compounds representing a broad range of organic molecules that constitute over 60% of drugs and agrochemicals in the market or research pipeline. Considering the vast abundance of these structural motifs, the development of chemical processes providing easy access to novel complex target molecules by introducing environmentally benign conditions with the main focus on improving the cost-effectiveness of the chemical transformation is highly demanding and challenging. Accordingly, sonochemistry appears to be an excellent alternative and a highly feasible environmentally benign energy input that has recently received considerable and steadily increasing interest in organic synthesis. However, the involvement of transition-metal-catalyst(s) in a chemical process often triggers an unintended impact on the greenness or sustainability of the transformation. Consequently, enormous efforts have been devoted to developing metal-free routes for assembling various heterocycles of medicinal interest, particularly under ultrasound irradiation. The present review article aims to demonstrate a brief overview of the current progress accomplished in the ultrasound-assisted synthesis of pharmaceutically relevant diverse heterocycles using transition-metal-free catalysis.

Sonochemistry in an organocatalytic domino reaction: an expedient multicomponent access to structurally functionalized dihydropyrano[3,2-b]pyrans, spiro-pyrano[3,2-b]pyrans, and spiro-indenoquinoxaline-pyranopyrans under ambient conditions

A highly convenient and sustainable one-pot approach for the diversely-oriented synthesis of a variety of medicinally privileged amino-substituted 4,8-dihydropyrano[3,2-b]pyran-3-carbonitriles, and spiro[indoline-3,4'-pyrano[3,2-b]pyran]-3-carbonitrile/carboxylate derivatives on the basis of a domino three-component reaction of readily available carbonyl compounds including aryl aldehydes or isatins, active methylene compounds, and kojic acid as a Michael donor using secondary amine catalyst l-proline under ultrasound irradiation in aqueous ethanolic solution at ambient temperature has been developed. This methodology can involve the assembly of C-C, C[double bond, length as m-dash]C, C-O, C-N bonds via a one-pot operation, and following this protocol, a series of novel amino-substituted spiro[indeno[1,2-b]quinoxaline-11,4-pyrano[3,2-b]pyran]-3-carbonitrile/carboxylates have been synthesized. The practical utility of this method was found to be very efficient for scale-up reaction and other useful transformations. The methodology provides significant advantages including mild reaction conditions, energy-efficiency, short reaction time, fast reaction, simple work-up procedure, broad functional group tolerances, utilization of reusable catalyst, green solvent system, being metal-free, ligand-free, waste-free, inexpensive, etc. Excellent chemical yields have been achieved without using column chromatography. To address the issues of green and more sustainable chemistry, several metrics including Atom Economy (AE), Reaction Mass Efficiency (RME), Atom efficiency, E-factor, Process Mass Intensity (PMI), and Carbon Efficiency (CE) have been quantified for the present methodology that indicates the greenness of the present protocol.

Recent advances in the transition-metal-free synthesis of quinoxalines

Quinoxalines, also known as benzo[a]pyrazines, constitute an important class of nitrogen-containing heterocyclic compounds as a result of their widespread prevalence in natural products, biologically active synthetic drug candidates, and optoelectronic materials. Owing to their importance and chemists' ever-increasing imagination of new transformations of these products, tremendous efforts have been dedicated to finding more efficient approaches toward the synthesis of quinoxaline rings. The last decades have witnessed a marvellous outburst in modifying organic synthetic methods to create them sustainable for the betterment of our environment. The exploitation of transition-metal-free catalysis in organic synthesis leads to a new frontier to access biologically active heterocycles and provides an alternative method from the perspective of green and sustainable chemistry. Despite notable developments achieved in transition-metal catalyzed synthesis, the high cost involved in the preparation of the catalyst, toxicity, and difficulty in removing it from the final products constitute disadvantageous effects on the atom economy and eco-friendly nature of the transformation. In this review article, we have summarized the recent progress achieved in the synthesis of quinoxalines under transition-metal-free conditions and cover the reports from 2015 to date. This aspect is presented alongside the mechanistic rationalization and limitations of the reaction methodologies. The scopes of future developments are also highlighted.