Organocatalyzed Synthesis and Antifungal Activity of Fully Substituted 1,4-Dihydropyridines

Synthesis, Cytotoxic Activity and In Silico Study of Novel Dihydropyridine Carboxylic Acids Derivatives

To aid the possible prevention of multidrug resistance in tumors and cause lower toxicity, a set of sixteen novel dihydropyridine carboxylic acids derivatives 3a-p were produced; thus, the activation of various ynones with triflic anhydride was performed, involving a nucleophilic addition of several bis(trimethylsilyl) ketene acetals, achieving good yields requiring easy workup. The target molecules were unequivocally characterized by common spectroscopic methods. In addition, two of the tested compounds (3a, and 3b) were selected to perform in silico studies due to the highest cytotoxic activity towards the HCT-15 cell line (7.94 ± 1.6 μM and 9.24 ± 0.9 μM, respectively). Employing theoretical calculations with density functional theory (DFT) using the B3LYP/6-311++G(d,p) showed that the molecular parameters correlate adequately with the experimental results. In contrast, predictions employing Osiris Property Explorer showed that compounds 3a and 3b present physicochemical characteristics that would likely make it an orally active drug. Moreover, the performance of Docking studies with proteins related to the apoptosis pathway allowed a proposal of which compounds could interact with PARP-1 protein. Pondering the obtained results (synthesis, in silico, and cytotoxic activity) of the target compounds, they can be judged as suitable antineoplastic agent candidates.

Binding Properties of Photosynthetic Herbicides: Photosynthetic Activity and Molecular Docking Approach towards 1,4-Dihydropyridines Derivatives

In the current work, we describe the synthesis of 1,4-dihydropyridine (1,4-DHP) derivatives via Hantzsch multicomponent reaction and their evaluation as photosystem II (PSII) inhibitors through chlorophyll a fluorescence bioassay. Among all the compounds tested, 1,1'-(2,4,6-trimethyl-1,4-dihydropyridine-3,5-diyl)bis(ethan-1-one) (4b) showed best results, reducing the parameters performance index on absorption basis (PI_abs ) and electron transport per reaction center by 61 % and 49 %, respectively, as compared to the control. These results indicate the inhibitory activity of PSII over the electron transport chain. Additionally, a molecular docking approach using the protein D1 (PDB code 4V82) was performed in order to assess the structure-activity relationship among the 1,4-DHP derivatives over the PSII, which revealed that both, size of the group at position 4 and the carbonyl groups at the dihydropyridine ring are important for the ligand's interaction, particularly for the hydrogen-bonding interaction with the residues His215, Ser264, and Phe265. Thus, the optimization of these molecular features is the aim of our research group to extend the knowledge of PSII electron chain inhibitors and the establishment of new potent bioactive molecular scaffolds.

Visible Light Mediated, Catalyst Free, One-Pot Convenient Synthesis of Dihydropyridines

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A simple, efficient and green protocol has been developed for the synthesis of polysubstituted dihydropyridines via one-pot, four-component reaction of aldehydes, arylamines, dialkyl acetylenedicarboxylate, and malononitrile. The reaction was proceeded at room temperature in the absence of catalyst in aqueous ethyl lactate under visible light irradiation. The main advantages of the present approach are mild reaction condition, high yield, no column chromatography, clean reaction profile, environmentally friendly and sustainable from the economic point of view

Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Background:

Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been used to accelerate organic transformations. With the development of environmental awareness, to obtain highly efficient scaffolds, scientists have directed their studies towards synthetic methodologies that minimize or preferably eliminate the formation of waste, avoid toxic solvents and reagents and use renewable starting materials as far as possible.

Methods:

In this connection, the organocatalytic reactions providing efficiency and selectivity for most of the transformations have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts contributing to the transformation of reactants into products with the least possible waste production, have been serving the concept of green chemistry.

Results and Conclusion:

Organocatalysts have been classified based on their binding capacity to the substrate with covalent or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol, and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.

α-Aminoazoles/azines: key reaction partners for multicomponent reactions

Aromatic α-aminoazaheterocycles are the focus of significant investigations and exploration by researchers owing to their key role in diverse biological and physiological processes. The existence of their derivatives in numerous drugs and alkaloids is due to their heterocyclic nitrogenous nature. Therefore, the synthesis of a structurally diverse range of their derivatives through simple and convenient methods represents a vital field of synthetic organic chemistry. Multicomponent reactions (MCRs) provide a platform to introduce desirable structure diversity and complexity into a molecule in a single operation with a significant reduction in the use of harmful organic waste, and hence have attracted particular attention as an excellent tool to access these derivatives. This review covers the advances made from 2010 to the beginning of 2020 in terms of the utilization of α-aminoazaheterocycles as synthetic precursors in MCRs.

An umpolung approach to the hydroboration of pyridines: a novel and efficient synthesis of N-H 1,4-dihydropyridines

The first inverse hydroboration of pyridine with a diboron(4) compound and a proton source has been realized under simple basic and catalyst-free conditions. This process consists of a formal boryl anion addition to pyridine, which produces an N-boryl pyridyl anion complex, and the subsequent protonation of the anion complex. This process enables a simple and efficient method for the synthesis of multi-substituted N-H 1,4-dihydropyridine (1,4-DHP) derivatives that are difficult to prepare using established methods. Furthermore, this method allows for facile preparation of 4-deuterated 1,4-DHPs from an easily accessible deuterium ion source. This inverse hydroboration reaction represents a new mode for pyridine functionalization.

Design, Synthesis, and Biological Evaluation of Novel Fused Spiro-4H-Pyran Derivatives as Bacterial Biofilm Disruptor

This study aims to synthesize novel fused spiro-4H-pyran derivatives under green conditions to develop agents having antimicrobial activity. The synthesized compounds were initially screened for in vitro antibacterial activity against two Gram-positive and three Gram-negative bacterial strains, and all the compounds exhibited moderate to potent antibacterial activity. However, compound 4l showed significant inhibition toward all the bacterial strains, particularly against Streptococcus pneumoniae and Escherichia coli with minimum inhibitory concentration values of 125 μg/mL for each. The toxicity studies of selected compounds (4c, 4e, 4l, and 4m) using human red blood cells as well as human embryonic kidney (HEK-293) cells showed nontoxic behavior at desired concentration. Growth kinetic and time-kill curve studies of 4l against S. pneumoniae and E. coli supported its bactericidal nature. Interestingly, compound 4l showed a synergistic effect when used in combination with ciprofloxacin against selected strains. Biofilm formation in the presence of a lead compound, as assessed by XTT assay, showed complete disruption of the bacterial biofilm visualized by scanning electron microscopy. Overall, the findings suggest 4l to be considered as a promising lead for further development as an antibacterial agent.

A catalyst- and solvent-free protocol for the sustainable synthesis of fused 4H-pyran derivatives

An efficient and cost-effective method was developed for the synthesis of two kinds of fused 4H-pyran derivatives, namely, dihydropyrano[2,3-c]pyrazole 4 and pyrano[3,2-c]chromenone 6. The reactions of 3-methyl-1-phenyl-5-pyrazolone/4-hydroxycoumarin with aromatic aldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine (NMSM), involving the Knoevenagel, Michael-addition, O-cyclization and elimination reactions under thermal heating, afforded the desired products. The synthesized compounds were characterized by standard spectroscopic techniques. Further, the structures of pyrazole-fused 4H-pyran 4a and coumarin-fused 4H-pyran 6b were confirmed by single-crystal XRD analysis. The short reaction time, good-to-excellent yields, elimination of the use of expensive, metallic and toxic catalysts or hazardous organic solvents and high atom-economy are some noteworthy features of this protocol.

A practical and greener method for the synthesis of highly functionalized pyrazole and coumarin fused 4H-pyran derivatives by exploring NMSM under neat conditions at 110 °C is described.

Microwave irradiation: a green approach for the synthesis of functionalizedN-methyl-1,4-dihydropyridines

An eco-friendly and cost-effective, microwave-assisted green approach has been developed for the synthesis of diverse functionalized N-methyl-1,4-dihydropyridines (1,4-DHPs). This pseudo three-component reaction was carried out between two equivalents of (E)-N-methyl-1-(methylthio)-2-nitroethenamine (NMSM) and one equivalent of aromatic aldehydes under microwave irradiation at 100 °C without catalyst and solvent. Short reaction times, avoidance of toxic solvents or expensive, metallic and corrosive catalysts and no need for column chromatographic purification are among the valuable features of the presented method. Moreover, the “greenness” of the method was evaluated within the ambits of the defined green metrics such as atom economy, carbon efficiency, E-factor, reaction mass efficiency, overall efficiency, process mass intensity and solvent intensity and the method exhibited a good to excellent score.

Microwave-assisted green synthesis of N-methyl-1,4-dihydropyridines under eco-friendly conditions.