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Molecules
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Five and Six-Membered Heterocyclic Compounds and Their Therapeutic Potential II
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Five and Six-Membered Heterocyclic Compounds and Their Therapeutic Potential II

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: 31 May 2024 | Viewed by 4471

Special Issue Editors

Prof. Dr. Mohamed Jawed Ahsan

E-Mail Website
Guest Editor
Department of Pharmaceutical Chemistry, Maharishi Arvind College of Pharmacy, Ambabari, Jaipur, Rajasthan 303 039, India
Interests: anticancer; antitubercular; green synthesis; medicinal chemistry; molecular docking; oxadiazoles; pyrazolines; pyrazoles
Special Issues, Collections and Topics in MDPI journals
Dr. Faizul Azam

E-Mail Website
Guest Editor
Department of Pharmaceutical Chemistry and Pharmacognosy, Unaizah College of Pharmacy, Qassim University, Uniazah 51911, Saudi Arabia
Interests: computational chemistry; molecular docking; molecular dynamics; DFT calculations
Special Issues, Collections and Topics in MDPI journals
Dr. Md. Afroz Bakht

E-Mail Website
Guest Editor
Department of Chemistry, College of Science and Humanity Studies, Prince Sattam Bin Abdulaziz University, P.O. Box- 83, Al-Kharj 11942, Saudi Arabia
Interests: catalysts; green synthesis; organic synthesis; nanoparticles; ultrasonic synthesis; ultrasonic extraction
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Five-membered heterocyclic compounds are appealing targets found in an extensive range of drug structures and have piqued the interest of medicinal chemists worldwide.

Many heterocyclic scaffolds can be considered privileged structures. Nitrogen, oxygen, and sulfur are the most prevalent heteroatoms found in heterocyclic compounds. According to statistics, a heterocycle is present in more than 85% of all biologically active chemical entities. Five-member heterocycles are classified as imidazoles, oxadiazoles, pyrazoles, thiadiazoles, triazoles, tetrazoles, and others depending on their number, nature, and arrangement of heteroatoms. They are crucial structural units in many pharmaceutical drugs, and can be found as an isolated ring or as a fused ring (e.g., benzimidazole, benzisoxazole, etc.).

Oxadiazole rings can be detected in drugs such as prenoxdiazine (cough suppressant), raltegravir (anti-HIV), and others, while the pyrazole heterocycle can be located in many NSAIDs (such as phenylbutazone, celecoxib, and others), antigout (sulfinpyrazone), and antipyretics (aminophenazone). The thiadiazole ring is found in acetazolamide, a diuretic and carbonic anhydrase inhibitor, and the imidazole ring is found in histamines, phenytoin, and other drugs.

This Special Issue attends to the following topics:

  1. Therapeutic potentials (anticancer, antitubercular, antimicrobial, anti-inflammatory, antioxidant, antiviral, etc.) of five-membered heterocycles.
  2. Conventional, microwave-assisted, and ultrasound-mediated synthesis of five-membered heterocycles.
  • The novel catalytic syntheses of five-membered heterocycles.
  1. Solvent-free and green synthesis of five-member heterocycles.
  2. In silico, molecular docking, molecular dynamics, and computational studies of five-membered heterocycles.
  3. Spectral characterization and DFT (HOMO and LUMO) studies of five-membered heterocycles.
  • Structural modification of natural isolates into their semi-synthetic analogues (five-membered heterocycles).

Thus, the current Special Issue aims to assemble and present recent advances in conventional and green synthesis, as well as their therapeutic applications related to five-membered heterocyclic compounds. The submission of communications, full papers, and reviews is most welcome.

Prof. Dr. Mohamed Jawed Ahsan
Dr. Faizul Azam
Dr. Md. Afroz Bakht
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • anti-Alzheimer
  • anticancer
  • antitubercular
  • catalysts
  • green synthesis
  • heterocyclic compounds
  • in silico studies
  • molecular docking
  • molecular dynamics
  • oxadiazoles
  • organic synthesis
  • pyrazoles
  • solvent free synthesis
  • thiadiazoles
  • ultrasonic and microwave synthesis
  • nanoparticles

Related Special Issue

Published Papers (3 papers)

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Research

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19 pages, 3709 KiB  
Article
Selective Generation of Aldimine and Ketimine Tautomers of the Schiff Base Condensates of Amino Acids with Imidazole Aldehydes or of Imidazole Methanamines with Pyruvates—Isomeric Control with 2- vs. 4-Substituted Imidazoles
by Greg Brewer, Cynthia Brewer, Raymond J. Butcher and Peter Zavalij
Molecules 2024, 29(6), 1324; https://doi.org/10.3390/molecules29061324 - 16 Mar 2024
Viewed by 455
Abstract
The Schiff base condensation of 5-methyl-4-imidazole carboxaldehyde, 5Me4ImCHO, and the anion of an amino acid, H2N-CH(R)CO2− (R = -CH3, -CH(CH3)2 and -CH2CH(CH3)2), gives the aldimine tautomer, Im-CH=N-CH(R)CO2 [...] Read more.
The Schiff base condensation of 5-methyl-4-imidazole carboxaldehyde, 5Me4ImCHO, and the anion of an amino acid, H2N-CH(R)CO2− (R = -CH3, -CH(CH3)2 and -CH2CH(CH3)2), gives the aldimine tautomer, Im-CH=N-CH(R)CO2−, while that of 5-methylimidazole-4-methanamine, 5MeIm-4-CH2NH2, with a 2-oxocarboxylate anion, R-C(O)-CO2−, gives the isomeric ketimine tautomer, Im-CH2-N=C(R)CO2−. All are isolated as the neutral nickel(II) complexes, NiL2, and are characterized by single crystal structure determination, IR, and positive ion ESI MS. In the cases of the 4 substituted imidazoles, either 5MeIm-4-CHO or 5MeIm-4-CH2NH2, both the aldimine and ketimine complexes are isolated cleanly with no evidence of an equilibrium between the two tautomers under the experimental conditions. The aldimines are blue while the tautomeric ketimines are green. In contrast, for the 2-substituted imidazoles, with either Im-2-CHO or Im-2-CH2NH2, the isolated product from the Schiff base condensation is the ketimine, which in the solid is green, as observed for the 4-isomer. These results suggest that for the 2-substituted imidazoles, there is a facile equilibrium between the aldimine and ketimine tautomers, and that the ketimine form is the thermodynamically favored tautomer. The aldimine tautomers of the 4-substituted imidazoles have three stereogenic centers, the nickel (Δ or Ʌ) and the two alpha carbon atoms (R or S). The observed pair of enantiomers is the ɅRR/ΔSS enantiomeric pair, suggesting that this pair is lower in energy than the others and that this is in general the preferred chiral correlation in these complexes. Full article
(This article belongs to the Special Issue Five and Six-Membered Heterocyclic Compounds and Their Therapeutic Potential II)
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16 pages, 2202 KiB  
Article
Synthesis, Anticancer Activity, and In Silico Studies of 5-(3-Bromophenyl)-N-aryl-4H-1,2,4-triazol-3-amine Analogs
by Mohamed Jawed Ahsan, Krishna Gautam, Amena Ali, Abuzer Ali, Abdulmalik Saleh Alfawaz Altamimi, Salahuddin, Manal A. Alossaimi, S. V. V. N. S. M. Lakshmi and Md. Faiyaz Ahsan
Molecules 2023, 28(19), 6936; https://doi.org/10.3390/molecules28196936 - 05 Oct 2023
Cited by 1 | Viewed by 1098
Abstract
In the current study, we described the synthesis of ten new 5-(3-Bromophenyl)-N-aryl-4H-1,2,4-triazol-3-amine analogs (4a–j), as well as their characterization, anticancer activity, molecular docking studies, ADME, and toxicity prediction. The title compounds (4a–j) were prepared in [...] Read more.
In the current study, we described the synthesis of ten new 5-(3-Bromophenyl)-N-aryl-4H-1,2,4-triazol-3-amine analogs (4a–j), as well as their characterization, anticancer activity, molecular docking studies, ADME, and toxicity prediction. The title compounds (4a–j) were prepared in three steps, starting from substituted anilines in a satisfactory yield, followed by their characterization via spectroscopic techniques. The National Cancer Institute (NCI US) protocol was followed to test the compounds’ (4a–j) anticancer activity against nine panels of 58 cancer cell lines at a concentration of 10−5 M, and growth percent (GP) as well as percent growth inhibition (PGI) were calculated. Some of the compounds demonstrated significant anticancer activity against a few cancer cell lines. The CNS cancer cell line SNB-75, which showed a PGI of 41.25 percent, was discovered to be the most sensitive cancer cell line to the tested compound 4e. The mean GP of compound 4i was found to be the most promising among the series of compounds. The five cancer cell lines that were found to be the most susceptible to compound 4i were SNB-75, UO-31, CCRF-CEM, EKVX, and OVCAR-5; these five cell lines showed PGIs of 38.94, 30.14, 26.92, 26.61, and 23.12 percent, respectively, at 10−5 M. The inhibition of tubulin is one of the primary molecular targets of many anticancer agents; hence, the compounds (4a–j) were further subjected to molecular docking studies looking at the tubulin–combretastatin A-4 binding site (PDB ID: 5LYJ) of tubulin. The binding affinities were found to be efficient, ranging from −6.502 to −8.341 kcal/mol, with two major electrostatic interactions observed: H-bond and halogen bond. Ligand 4i had a binding affinity of −8.149 kcal/mol with the tubulin–combretastatin A-4 binding site and displayed a H-bond interaction with the residue Asn258. The ADME and toxicity prediction studies for each compound were carried out using SwissADME and ProTox-II software. None of the compounds’ ADME predictions showed that they violated Lipinski’s rule of five. All of the compounds were also predicted to have LD50 values between 440 and 500 mg/kg, putting them all in class IV toxicity, according to the toxicity prediction. The current discovery could potentially open up the opportunity for further developments in cancer. Full article
(This article belongs to the Special Issue Five and Six-Membered Heterocyclic Compounds and Their Therapeutic Potential II)
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Review

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53 pages, 10112 KiB  
Review
A Review on Five and Six-Membered Heterocyclic Compounds Targeting the Penicillin-Binding Protein 2 (PBP2A) of Methicillin-Resistant Staphylococcus aureus (MRSA)
by Shraddha S. Ambade, Vivek Kumar Gupta, Ritesh P. Bhole, Pramod B. Khedekar and Rupesh V. Chikhale
Molecules 2023, 28(20), 7008; https://doi.org/10.3390/molecules28207008 - 10 Oct 2023
Cited by 2 | Viewed by 2226
Abstract
Staphylococcus aureus is a common human pathogen. Methicillin-resistant Staphylococcus aureus (MRSA) infections pose significant and challenging therapeutic difficulties. MRSA often acquires the non-native gene PBP2a, which results in reduced susceptibility to β-lactam antibiotics, thus conferring resistance. PBP2a has a lower affinity for methicillin, [...] Read more.
Staphylococcus aureus is a common human pathogen. Methicillin-resistant Staphylococcus aureus (MRSA) infections pose significant and challenging therapeutic difficulties. MRSA often acquires the non-native gene PBP2a, which results in reduced susceptibility to β-lactam antibiotics, thus conferring resistance. PBP2a has a lower affinity for methicillin, allowing bacteria to maintain peptidoglycan biosynthesis, a core component of the bacterial cell wall. Consequently, even in the presence of methicillin or other antibiotics, bacteria can develop resistance. Due to genes responsible for resistance, S. aureus becomes MRSA. The fundamental premise of this resistance mechanism is well-understood. Given the therapeutic concerns posed by resistant microorganisms, there is a legitimate demand for novel antibiotics. This review primarily focuses on PBP2a scaffolds and the various screening approaches used to identify PBP2a inhibitors. The following classes of compounds and their biological activities are discussed: Penicillin, Cephalosporins, Pyrazole-Benzimidazole-based derivatives, Oxadiazole-containing derivatives, non-β-lactam allosteric inhibitors, 4-(3H)-Quinazolinones, Pyrrolylated chalcone, Bis-2-Oxoazetidinyl macrocycles (β-lactam antibiotics with 1,3-Bridges), Macrocycle-embedded β-lactams as novel inhibitors, Pyridine-Coupled Pyrimidinones, novel Naphthalimide corbelled aminothiazoximes, non-covalent inhibitors, Investigational-β-lactam antibiotics, Carbapenem, novel Benzoxazole derivatives, Pyrazolylpyridine analogues, and other miscellaneous classes of scaffolds for PBP2a. Additionally, we discuss the penicillin-binding protein, a crucial target in the MRSA cell wall. Various aspects of PBP2a, bacterial cell walls, peptidoglycans, different crystal structures of PBP2a, synthetic routes for PBP2a inhibitors, and future perspectives on MRSA inhibitors are also explored. Full article
(This article belongs to the Special Issue Five and Six-Membered Heterocyclic Compounds and Their Therapeutic Potential II)
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