Spiro indolinone beta-lactams, inhibitors of poliovirus and rhinovlrus 3C-proteinases

Antioxidant and Antimicrobial Potential of 1,8-Naphthyridine Based Scaffolds: Design, Synthesis and in Silico Simulation Studies within Topoisomerase II

A series of spiro β-Lactams (4 a-c, 7 a-c) and thiazolidinones (5 a-c, 8 a-c) possessing 1,8-naphthyridine moiety were synthesized in this study. The structure of the newly synthesized compounds has been confirmed by IR, 1H-NMR, 13C NMR, mass spectra, and elemental analysis. The synthesized compounds were tested in vitro for their antibacterial and antifungal activity against various strains. The antimicrobial data showed that most of the compounds displayed good efficacy against both bacteria and fungi. The structure-activity relationship (SAR) studies suggested that the presence of electron-withdrawing chloro (3 b, 4 b, and 5 b) and nitro groups (7 b, 8 b) at the para position of the phenyl ring improved the antimicrobial activity of the compounds. The free radical scavenging assay showed that all the synthesized compounds exhibited significant antioxidant activity on DPPH. Compounds 8 b (IC50=17.68±0.76 μg/mL) and 4 c (IC50=18.53±0.52 μg/mL) showed the highest antioxidant activity compared to ascorbic acid (IC50=15.16±0.43 μg/mL). Molecular docking studies were also conducted to support the antimicrobial and SAR results.

Thiophene-fused γ-lactams inhibit the SARS-CoV-2 main protease via reversible covalent acylation

Enzyme inhibitors working by O-acylation of nucleophilic serine residues are of immense medicinal importance, as exemplified by the β-lactam antibiotics. By contrast, inhibition of nucleophilic cysteine enzymes by S-acylation has not been widely exploited for medicinal applications. The SARS-CoV-2 main protease (Mpro) is a nucleophilic cysteine protease and a validated therapeutic target for COVID-19 treatment using small-molecule inhibitors. The clinically used Mpro inhibitors nirmatrelvir and simnotrelvir work via reversible covalent reaction of their electrophilic nitrile with the Mpro nucleophilic cysteine (Cys145). We report combined structure activity relationship and mass spectrometric studies revealing that appropriately functionalized γ-lactams can potently inhibit Mpro by reversible covalent reaction with Cys145 of Mpro. The results suggest that γ-lactams have potential as electrophilic warheads for development of covalently reacting small-molecule inhibitors of Mpro and, by implication, other nucleophilic cysteine enzymes.

Rapid Access to Chiral Spiro[2.3] Lactams: Stereoselective Hydroborylation and Hydrosilylation and Remote Control of Axial Chirality by Copper-Catalyzed Desymmetrization of Spirocyclopropenes

Chiral spirocyclopropyl β-lactams are common motifs in bioactive compounds and pharmaceuticals. Here we disclose a diastereoselective and enantioselective hydroborylation and hydrosilylation of spirocyclopropenes, via a Cu-catalyzed desymmetrization strategy, for the rapid preparation of enantio-enriched spirocyclopropyl β-lactams. The efficient desymmetrization strategy allows the remote control of axial chirality, offering the borylated and silylated products bearing central, spiro, and axial chirality. The combination of multichiral elements would provide a novel motif for biological evaluation in potential drug discovery.

Organocatalytic Asymmetric [4 + 2]-Cycloadditions of 2-Aminophenyl Enones with Isatin-Derived Ketimines: Diastereo- and Enantioselective Synthesis of Spirooxindole-Tetrahydroquinazolines

A novel method for the enantioselective synthesis of spiro N,N-heterocyclic oxindoles has been developed, employing asymmetric [4 + 2]-cycloadditions of 2-aminophenyl enones with isatin-derived ketimines. This method employs an organocatalytic approach, utilizing a bifunctional squaramide-based catalyst. It enables the precise synthesis of chiral spirooxindole-tetrahydroquinazolines with intricate structures, featuring chiral quaternary centers. This process achieves remarkable results, including high yields and exceptional levels of enantioselectivity and diastereoselectivity (up to 96% yield, 95% ee, and >20:1 dr).

Small Molecules with Spiro-Conjugated Cycles: Advances in Synthesis and Applications

Dear Colleagues, [...].

COVID-19 therapeutics: small-molecule drug development targeting SARS-CoV-2 main protease

The severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is the causative factor behind the 2019 global coronavirus pandemic (COVID-19). The main protease, known as M^pro, is encoded by the viral genome and is essential for viral replication. It has also been an effective target for drug development. In this review, we discuss the rationale for inhibitors that specifically target SARS-CoV-2 M^pro. Small molecules and peptidomimetic inhibitors are two types of inhibitor with various modes of action and we focus here on novel inhibitors that were only discovered during the COVID-19 pandemic highlighting their binding modes and structures.

Penicillin Derivatives Inhibit the SARS-CoV-2 Main Protease by Reaction with Its Nucleophilic Cysteine

The SARS-CoV-2 main protease (Mpro) is a medicinal chemistry target for COVID-19 treatment. Given the clinical efficacy of β-lactams as inhibitors of bacterial nucleophilic enzymes, they are of interest as inhibitors of viral nucleophilic serine and cysteine proteases. We describe the synthesis of penicillin derivatives which are potent Mpro inhibitors and investigate their mechanism of inhibition using mass spectrometric and crystallographic analyses. The results suggest that β-lactams have considerable potential as Mpro inhibitors via a mechanism involving reaction with the nucleophilic cysteine to form a stable acyl-enzyme complex as shown by crystallographic analysis. The results highlight the potential for inhibition of viral proteases employing nucleophilic catalysis by β-lactams and related acylating agents.

New Methods for the Synthesis of Spirocyclic Cephalosporin Analogues

Spiro compounds provide attractive targets in drug discovery due to their inherent three-dimensional structures, which enhance protein interactions, aid solubility and facilitate molecular modelling. However, synthetic methodology for the spiro-functionalisation of important classes of penicillin and cephalosporin β-lactam antibiotics is comparatively limited. We report a novel method for the generation of spiro-cephalosporin compounds through a Michael-type addition to the dihydrothiazine ring. Coupling of a range of catechols is achieved under mildly basic conditions (K2CO3, DMF), giving the stereoselective formation of spiro-cephalosporins (d.r. 14:1 to 8:1) in moderate to good yields (28-65%).

Design, Synthesis, Docking and Biological Evaluation of Novel 4-hydroxy Coumarin Derivatives

BACKGROUND

Hospital-acquired (HA) infections are caused due to E. coli, which is resistant to multiple drugs particularly to fluoroquinolone class of drugs. Urinary tract infections (UTI) affects people in the community and hospitals. 150 million people per annum are suffering from UTI worldwide.

METHODS

In this present study, we designed 36 novel coumarin derivatives, also we predicted pharmacokinetic and toxicity parameters. Docking studies were also carried out and all the compounds were evaluated for antibacterial activity against resistant quinolone E. coli strain ATCC 25922. It was interesting to note that the introduction of electron-withdrawing group on the aromatic ring resulted in compounds with an increased antibacterial activity, which is observed in compound 6 (with 4-nitro substitution), compound 23 (chloro) and compound 30 (chloro, nitro).

RESULTS

From the MIC results, it was observed that compounds 6, 23 and 30 showed higher activity with 0.5μg/ml, 0. 12 μg/ml, 0.5 μg/ml respectively. Docking studies were performed with the active site of DNA gyrase (PDB ID: 4CKK). The maximum binding energy was found to be -10.7 Kcal/mol.

CONCLUSION

From the study, it was found that 3 compounds were potentially active against quinolone- resistant E. coli strains. This study can further be extended for in vivo evaluation.

Diastereoselective [3 + 1] Cyclization Reaction of Oxindolyl Azaoxyallyl Cations with Sulfur Ylides: Assembly of 3,3'-Spiro[β-lactam]-oxindoles

Oxindoles and β-lactams are attractive structural motifs because of their unique biological importance. However, the fusion of the two moieties featuring 3,3'-spirocyclic scaffolds is a challenging task in organic synthesis. Herein we designed a novel type of oxindole-based azaoxyallyl cation synthons, which could readily participate in the [3 + 1] cyclization with sulfur ylides. With this protocol, a collection of 3,3-spiro[β-lactam]-oxindoles were facilely produced in up to 94% yield with perfect diastereoselectivity.

Spiro-β-lactam BSS-730A Displays Potent Activity against HIV and Plasmodium

The high burden of malaria and HIV/AIDS prevents economic and social progress in developing countries. A continuing need exists for development of novel drugs and treatment regimens for both diseases in order to address the tolerability and long-term safety concerns associated with current treatment options and the emergence of drug resistance. We describe new spiro-β-lactam derivatives with potent (nM) activity against HIV and Plasmodium and no activity against bacteria and yeast. The best performing molecule of the series, BSS-730A, inhibited both HIV-1 and HIV-2 replication with an IC₅₀ of 13 ± 9.59 nM and P. berghei hepatic infection with an IC₅₀ of 0.55 ± 0.14 μM with a clear impact on parasite development. BSS-730A was also active against the erythrocytic stages of P. falciparum, with an estimated IC₅₀ of 0.43 ± 0.04 μM. Time-of-addition studies showed that BSS-730A potentially affects all stages of the HIV replicative cycle, suggesting a complex mechanism of action. BSS-730A was active against multidrug-resistant HIV isolates, with a median 2.4-fold higher IC₅₀ relative to control isolates. BSS-730A was equally active against R5 and X4 HIV isolates and displayed strong synergism with the entry inhibitor AMD3100. BSS-730A is a promising candidate for development as a potential therapeutic and/or prophylactic agent against HIV and Plasmodium.

Stereoselective synthesis and applications of spirocyclic oxindoles

This review summaries recent synthetic developments towards spirocyclic oxindoles and applications as valuable medicinal and synthetic targets.

A [3 + 2] cycloaddition/C-arylation of isatin N,N′-cyclic azomethine imine 1,3-dipole with arynes

A [3 + 2] annulation/C-arylation reaction of 1,3-dipole 1 with arynes has been established for the synthesis of oxindole scaffolds.

Synthesis of 1,3-diaryl-spiro[azetidine-2,3′-indoline]-2′,4-dionesviathe Staudinger reaction:cis- ortrans-diastereoselectivity with different addition modes

A new synthetic approach for realizing biologically relevant bis-aryl spiro[azetidine-2,3′-indoline]-2′,4-diones was developed based on Staudinger ketene–imine cycloaddition through the one-pot reaction of substituted acetic acids and Schiff bases in the presence of oxalyl chloride and an organic base. A series of [azetidine-2,3′-indoline]-2′,4-diones were synthesized using this method. For comparison, the same compounds were obtained using a known technique, where ketene is generated from pre-synthesized acyl chloride. It was shown that the use of oxalyl chloride for ketene generation in the one-pot reaction at room temperature allows for the reversal of the diastereoselectivity of spiro-lactam formation, unlike previously described procedures.

Two experimental techniques of the ketene–imine Staudinger reaction allowed different diastereomers of spiro-indolinone-β-lactams to be obtained.

Montmorillonite Catalysed Synthesis of Novel Spiro[3H-Indole-3,3′- [3H-1,2,4] Triazol]-2(1H) Ones in Dry Media under Microwave Irradiation

A new route for the one pot synthesis of novel spiro[3H-indole-3,3′-[3H-1,2,4] triazol]-2 (1H) ones utilizing 3-arylimino-2H-indol-2-ones (3) and thiosemicarbazide (4) as starting material under microwave irradiation is reported. Complete conversion was observed by TLC which also showed the formation of a single product.

Synthesis of New Bis(spiro-β-lactams) via Interaction of Methyl 1-Bromocycloalcanecarboxylates with Zinc and N,N′-Bis(arylmethylidene)benzidines

Interaction of the Reformatsky reagents, prepared from methyl 1-bromocyclopentane-1-carboxylate or methyl 1-bromocyclohexane-1-carboxylate, with N,N′-bis(arylmethylidene)benzidines has given rise to a set of intermediates as a result of nucleophilic addition to the C=N group of a substrate. Further intramolecular attack of the amide nitrogen atom onto the ester carbonyl group is responsible for the ring closure, which affords two series of spirocompounds: 2,2′-([1,1′-biphenyl]-4,4′-diyl)bis(3-aryl-2-azaspiro[3.4]octan-1-one) or 2,2′-([1,1′-biphenyl]-4,4′-diyl)bis(3-aryl-2-azaspiro[3.5]nonan-1-ones).

Thermal-mediated catalyst-free heterolytic cleavage of 3-halooxindoles: rapid access to 3-functionalized-2-oxindoles

Herein a previously unreported catalyst-free S_N1 reaction of the 3-halooxindoles to build 3-functionalized-2-oxindoles is described.

Optimization of a β-Lactam Scaffold for Antibacterial Activity via the Inhibition of Bacterial Type I Signal Peptidase

β-Lactam antibiotics, one of the most important class of human therapeutics, act via the inhibition of penicillin-binding proteins (PBPs). The unparalleled success in their development has inspired efforts to develop them as inhibitors of other targets. Bacterial type I signal peptidase is evolutionarily related to the PBPs, but the stereochemistry of its substrates and its catalytic mechanism suggest that β-lactams with the 5S stereochemistry, as opposed to the 5R stereochemistry of the traditional β-lactams, would be required for inhibition. We report the synthesis and evaluation of a variety of 5S penem derivatives and identify several with promising activity against both a Gram-positive and a Gram-negative bacterial pathogen. To our knowledge these are the first 5S β-lactams to possess significant antibacterial activity and the first β-lactams imparted with antibacterial activity via optimization of the inhibition of a target other than a PBP. Along with the privileged status of their scaffold and the promise of bacterial signal peptidase I (SPase) as a target, this activity makes these compounds promising leads for development as novel therapeutics.

Facile access to regio- and stereoselective synthesis of highly functionalized spiro[indoline-3,2′-pyrrolidines] incorporating a pyrene moiety: experimental, photophysical and theoretical approach

The regio- and stereochemical polar [3 + 2] cycloaddition of azomethine ylides, which were generated in situ by the reaction of isatin and sarcosine or benzylamine, with (E)-3-aryl-1-(pyren-1-yl)prop-2-en-1-ones as dipolarophiles, was studied using experimental and theoretical methods. The chemical structures and relative configurations of all products have been fully established by 1D and 2D homonuclear and heteronuclear correlation NMR spectrometry. The effects of the electronic and steric factors of the reactions were discussed. The photophysical properties of the synthesized spiro[indoline-3,2′-pyrrolidin]-2-ones and 5′-phenyl-spiro[indoline-3,2′-pyrrolidin]-2-ones were studied. The mechanism of the reactions was investigated using global and local reactivity indices and frontier molecular orbital (FMO) analysis at the B3LYP/6-31G level of theory. The relationship between the electrophilicity index ω of the dipolarophiles and the Hammett constant σ_p has been studied. The theoretical scale of reactivity correctly explains the electrophilic activation/deactivation effects promoted by electron-withdrawing and electron-releasing substituents in the para-position of the dipolarophiles.

The regio- and stereochemical polar [3 + 2] cycloaddition of azomethine ylides with (E)-3-aryl-1-(pyren-1-yl)prop-2-en-1-ones as dipolarophiles, was studied using experimental and theoretical methods.

An asymmetric acetate-Mannich reaction of chiral isatin derived ketimines and its applications

A highly efficient TMSOTf-mediated asymmetric acetate-Mannich reaction of isatin derived tert-butylsulfinyl ketimines and S-phenyl thioacetate was developed to afford the direct synthesis of indole-based β^3,3-amino acid thioester with excellent selectivity (dr > 98 : 2). Syntheses of (+)-AG-041R and 3-aminopyrroloindoline have been accomplished utilizing the developed method.

A novel one-pot green synthesis of dispirooxindolo-pyrrolidines via 1,3-dipolar cycloaddition reactions of azomethine ylides

A facile synthesis of dispirooxindolopyrrolidines has been accomplished via a one-pot three component 1,3-dipolar cycloaddition reaction. The reaction of azomethine ylides generated in situ from L-phenylalanine and substituted isatins with a series of unusual (E)-2-oxoindolino-3-ylidene acetophenone dipolarophiles in the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]BF4, furnished the cycloadducts in good yields, with the regioisomers 5a-f being obtained with high selectivity. Furthermore, the recyclability of [bmim]BF4, up to five times, was also investigated.

Environ-Economic Synthesis and Characterization of Some New 1,2,4-Triazole Derivatives as Organic Fluorescent Materials and Potent Fungicidal Agents

A multicomponent one-pot clean cyclocondensation reaction of 4-chloro-2-nitro aniline/amino acids and aromatic aldehydes/indole-2,3-diones with thiosemicarbazide in water yielding triazole/spiro indole-triazole derivatives in high yields and shorter reaction time and displaying excellent florescent property is reported. The developed MCR may provide a valuable practical tool for the synthesis of new drugs containing the title core fragment. All the newly synthesized compounds have been characterized by IR, 1HNMR, 13CNMR, and fluorescence study and also been screened for antimicrobial activity.