Synthesis of indolequinones via a Sonogashira coupling/cyclization cascade reaction

Structure-Activity Relationship Studies of Antimicrobial Naphthoquinones Derived from Constituents of Tabebuia avellanedae

In this study, based on our previous study, derivatives of naphtho[2,3-b]furan-4,9-diones were synthesized and their antimicrobial activities were evaluated. The screening of these naphthoquinones revealed that the fluorine-containing NQ008 compound exhibited potent and broad antimicrobial activities against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative bacteria, and fungi. The results of the ratio of the minimum bactericidal concentration (MBC) to the minimum inhibitory concentrations (MICs) and time-kill assays suggest that the mode of action of NQ008 is bactericidal. Additionally, the results of a drug resistance study revealed that NQ008 exhibited potent antibacterial activity and may delay the development of bacteria resistance. Furthermore, NQ008 exhibited preliminary antiviral activity against the swine influenza virus and Feline calicivirus.

Synthesis, In Vitro and In Silico Studies of Indolequinone Derivatives against Clinically Relevant Bacterial Pathogens

Background:

According to the World Health Organization, antimicrobial resistance is one of the most important public health threats of the 21st century. Therefore, there is an urgent need for the development of antimicrobial agents with new mechanism of action, especially those capable of evading known resistance mechanisms.

Objective:

We described the synthesis, in vitro antimicrobial evaluation, and in silico analysis of a series of 1H-indole-4,7-dione derivatives.

Methods:

The new series of 1H-indole-4,7-diones was prepared with good yield by using a copper(II)- mediated reaction between bromoquinone and β-enamino ketones bearing alkyl or phenyl groups attached to the nitrogen atom. The antimicrobial potential of indole derivatives was assessed. Molecular docking studies were also performed using AutoDock 4.2 for Windows. Characterization of all compounds was confirmed by one- and two-dimensional NMR techniques 1H and 13C NMR spectra [1H, 13C – APT, 1H x 1H – COSY, HSQC and HMBC], IR and mass spectrometry analysis.

Results:

Several indolequinone compounds showed effective antimicrobial profile against Grampositive (MIC = 16 µg.mL-1) and Gram-negative bacteria (MIC = 8 µg.mL-1) similar to antimicrobials current on the market. The 3-acetyl-1-(2,5-dimethylphenyl)-1H-indole-4,7-dione derivative exhibited an important effect against different biofilm stages formed by a serious hospital life-threatening resistant strain of Methicillin-Resistant Staphylococcus aureus (MRSA). A hemocompatibility profile analysis based on in vitro hemolysis assays revealed the low toxicity effects of this new series. Indeed, in silico studies showed a good pharmacokinetics and toxicological profiles for all indolequinone derivatives, reinforcing their feasibility to display a promising oral bioavailability. An elucidation of the promising indolequinone derivatives binding mode was achieved, showing interactions with important sites to biological activity of S. aureus DNA gyrase. These results highlighted 3-acetyl-1-(2-hydroxyethyl)-1Hindole- 4,7-dione derivative as broad-spectrum antimicrobial prototype to be further explored for treating bacterial infections.

Conclusion:

The highly substituted indolequinones were obtained in moderate to good yields. The pharmacological study indicated that these compounds should be exploited in the search for a leading substance in a project aimed at obtaining new antimicrobials effective against Gram-negative bacteria.

Ultrasound assisted one-pot synthesis of benzo-fused indole-4, 9-dinones from 1,4-naphthoquinone and α-aminoacetals

A one-pot synthesis of benzo[f]indole-4,9-diones from 1,4-naphthoquinone with α-aminoacetals has been developed. This method provides a straightforward synthesis of benzo[f]indole-4,9-diones via intramolecular nucleophilic attack of aminoquinones to aldehydes under mild reaction conditions. The detailed mechanism was also investigated.

Copper(II)-Mediated Synthesis of Indolequinones from Bromoquinones and Enamines

The reaction of enamines and bromoquinones in the presence of copper(II) acetate and potassium carbonate results in a regiospecific synthesis of indolequinones. The reaction is broad in scope and scalable and provides a route to the core structure that is present in several biologically interesting natural and synthetic compounds.

Bifunctionalisation of 1,4-naphthoquinone by the Oxidative Addition of an Alkylamine and Iodine

Novel 2-iodo-3-(alkylamino) naphthalene-1,4-diones are formed in 33–70% yield by the reaction of alkylamine and 1, 4-naphthoquinone in the presence of iodine.

One-pot synthesis of benzo[f]indole-4,9-diones from 1,4-naphthoquinones and terminal acetylenes

In this paper, a concise one-pot method for the construction of benzo[f]indole-4,9-dione motifs is described. These transformations proceed via a sequential palladium- and copper-catalyzed coupling reaction of 1,4-naphthoquinones with terminal acetylenes, followed by a copper-catalyzed intramolecular cyclization reaction of the resulting coupling product.