Glycerol assisted eco-friendly strategy for the facile synthesis of 4,4′-(arylmethylene)bis(3-methyl-1H-pyrazol-5-ols) and 2-aryl-2,3-dihydroquinazolin-4(1H)-ones under catalyst-free conditions

Wang resin catalysed sonochemical synthesis of pyrazolo[4,3-d]pyrimidinones and 2,3-dihydroquinazolin-4(1H)-ones: Identification of chorismate mutase inhibitors having effects on Mycobacterium tuberculosis cell viability

The enzyme chorismate mutase (or CM that is vital for the survival of bacteria) is an interesting pharmacological target for the identification of new anti-tubercular agents. The 5,5-disibstituted pyrazolo[4,3-d]pyrimidinone derivatives containing the fragment based on 4-amino-1-methyl-3-propyl-1H-pyrazole-5-carboxamide were designed and explored as the potential inhibitors of chorismate mutase. Based on encouraging docking results of two representative molecules evaluated in silico against MtbCM (PDB: 2FP2) the Wang resin catalysed sonochemical synthesis of target N-heteroarenes were undertaken. The methodology involved the reaction of 4-amino-1-methyl-3-propyl-1H-pyrazole-5-carboxamide with the appropriate cyclic/acyclic ketones to afford the desired products in acceptable (51-94%) yields. The methodology was also extended successfully towards the synthesis of 2,2-disubstituted 2,3-dihydroquinazolin-4(1H)-ones in excellent (85-90%) yields. In vitro MTT assay against the RAW 264.7 cell line followed by enzymatic assay against MtbCM identified 3b and 3c as active compounds that showed two H-bonding via their NH (at position 6) and CO group with MtbCM in silico and encouraging (54-57%) inhibition at 30 µM in vitro. Notably, none of the 2,2-disubstituted 2,3-dihydroquinazolin-4(1H)-ones showed any significant inhibition of MtbCM suggesting the favourable role of the pyrazole moiety in case of pyrazolo[4,3-d]pyrimidinones. The favourable role of cyclopentyl ring attached to the pyrazolo[4,3-d]pyrimidinone moiety and that of two methyl groups in place of cyclopentyl ring was also indicated by the SAR study. Besides showing effects against MtbCM in the concentration response study, 3b and 3c showed little or no effects on mammalian cell viability up to 100 µM in an MTT assay but decreased the % Mtb cell viability at 10-30 µM with > 20% decrease at 30 µM in an Alamar Blue Assay. Moreover, no adverse effects were noted for these compounds when tested for teratogenicity and hepatotoxicity in zebrafish at various concentrations. Overall, being the only example of MtbCM inhibitors that showed effects on Mtb cell viability the compound 3b and 3c are of further interest form the view point of discovery and development of new anti-tubercular agents.

Pyrazolone-type compounds (part II): in vitro and in silico evaluation of antioxidant potential; structure-activity relationship

The pyrazolone class comprises a variety of hybrid compounds displaying diverse biological actions. Although studied for decades, these compounds are still of interest due to their facile chemical transformations. In our previous work, we presented the synthetic route of functionalised pyrazolone derivatives. The presence of pyrazolone structural motif in many drugs, such as edaravone, prompted us to investigate the antioxidant features of the selected compounds. In this paper, we provide an extensive in vitro and in silico description of the antioxidant properties of selected pyrazolone analogues. The obtained in vitro results revealed their great antiradical potency against the DPPH radical (IC50 values in the 2.6-7.8 μM range), where the best results were obtained for analogues bearing a catechol moiety. Density functional theory (DFT) was used to assess their antioxidant capacity from the thermodynamic aspect. Here, good agreement with in vitro results was achieved. DFT was employed for the prediction of the most preferable radical scavenging pathway, also. In polar solvents, the SPLET mechanism is a favourable scavenging route, whereas in nonpolar solvents the HAT is slightly predominant. Furthermore, antioxidant mechanisms were studied in the presence of relevant reactive oxygen species. The obtained values of the reaction enthalpies with the selected radicals revealed that HAT is slightly prevailing in polar solvents, while the SPLET mechanism is dominant in nonpolar solvents. Regarding the well-known antioxidant features of the drug edaravone, these findings represent valuable data for this pyrazolone class and could be used as the basis for further investigations.

Pyrazolone-type compounds: synthesis and in silico assessment of antiviral potential against key viral proteins of SARS-CoV-2

Coronavirus outbreak is still a major public health concern. The high mutation ability of SARS-CoV-2 periodically delivers more transmissible and dangerous variants. Hence, the necessity for an efficient and inexpensive antiviral agent is urgent. In this work, pyrazolone-type compounds were synthesised, characterised using spectroscopic methods and theoretical tools, and evaluated in silico against proteins of SARS-CoV-2 responsible for host cell entry and reproduction processes, i.e., spike protein (S), Mpro, and PLpro. Five of twenty compounds are newly synthesised. In addition, the crystal structure of a pyrazolone derivative bearing a vanillin moiety is determined. The obtained in silico results indicate a more favourable binding affinity of pyrazolone analogues towards Mpro, and PLpro in comparison to drugs lopinavir, remdesivir, chloroquine, and favipiravir, while in the case of S protein only lopinavir exerted higher binding affinity. Also, the investigations were performed on ACE2 and the spike RBD-ACE2 complex. The obtained results for these proteins suggest that selected compounds could express antiviral properties by blocking the binding to the host cell and viral spreading, also. Moreover, several derivatives expressed multitarget antiviral action, blocking both binding and reproduction processes. Additionally, in silico ADME/T calculations predicted favourable features of the synthesised compounds, i.e., drug-likeness, oral bioavailability, as well as good pharmacokinetic parameters related to absorption, metabolism, and toxicity. The obtained results imply the great potential of synthesised pyrazolones as multitarget agents against SARS-CoV-2 and represent a valuable background for further in vitro investigations.

An Aqueous Facile Synthesis of 2,3-Dihydroquinazolin-4(1H)-One Derivatives by Reverse Zinc Oxide Micelles as Nanoreactor

A green synthetic protocol has been developed for the efficient preparation of 2,3-dihydroquinazolin−4(1H)-one derivatives with excellent yield in aqueous media. Reverse zinc oxide micelles catalyzed the reactions efficiently and selectively as the hallow nanoreactor. Moreover, the catalyst was reusable without significant loss of catalytic efficiency. The notable advantages of the procedure are high yields and mild reaction conditions, simple operation, nonchromatographic purification, environmentally friendly and good versatile substrates.

Mekheimer R, M. Hayallah A, A. Abo Elsoud F, U. Sadek K. Recent Advances in the Utility of Glycerol as a Benign and Biodegradable Medium in Heterocyclic Synthesis

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Glycerol is a non-toxic, recyclable and biodegradable organic waste produced as a byproduct in the production of biodiesel fuel. Currently, glycerol is considered a green solvent and catalyst for a large variety of applications. This work discusses the significance of glycerol for heterocyclic synthesis. All the reported studies consider glycerol as an efficient and sustainable benign medium.

Praseodymium(iii) anchored on CoFe2O4 MNPs: an efficient heterogeneous magnetic nanocatalyst for one-pot, multi-component domino synthesis of polyhydroquinoline and 2,3-dihydroquinazolin-4(1H)-one derivatives

CoFe₂O₄@Pr as highly efficient and reusable heterogeneous catalyst prepared by a simple procedure for the synthesis of polyhydroquinoline and 2,3-dihydroquinazolin-4(1H)-one derivatives.

2,3-Dihydroquinazolin-4(1H)-one as a privileged scaffold in drug design

2,3-Dihydroquinazolin-4-one (DHQ) belongs to the class of nitrogen-containing heterocyclic compounds representing a core structural component in various biologically active compounds. In the past decades, several methodologies have been developed for the synthesis of the DHQ framework, especially the 2-substituted derivatives. Unfortunately, multistep syntheses, harsh reaction conditions, and the use of toxic reagents and solvents have limited their full potential as a versatile fragment. Recently, use of green chemistry and alternative strategies are being explored to prepare diverse DHQ derivatives. This fragment is used as a synthon for the preparation of biologically active quinazolinones and as a functional substrate for the synthesis of modified DHQ derivatives exhibiting different biological properties. In this review, we provide a comprehensive assessment of the synthesis and biological evaluations of DHQ derivatives.

Efficient Preparation of Potassium Arylmethylene-4-(1H-Pyrazol-5-ol)-4′-(1H-Pyrazol-5-Olate) Derivatives via a Four-Component Reaction

A four-component reaction was investigated to prepare potassium arylmethylene-4-(1 H-pyrazol-5-ol)-4′-(1 H-pyrazol-5-olate) derivatives from dialkyl but-2-ynedioates, phenylhydrazine, substituted benzaldehydes and potassium carbonate without any catalyst or promoter. The structure of a typical product was confirmed by X-ray crystallography. The advantages of the present methodology are efficiency, broad scope, operational simplicity, high yields and mild reaction conditions.

A practical green approach to diversified spirochromene/spiropyran scaffolds via a glucose–water synergy driven organocatalytic system

Development of a versatile, new glucose–water organocatalytic system promoted, one pot, practical green method for the synthesis of diversified spirochromenes/spiropyrans is reported.