- Kinetics and Mechanism of Bioactivation via S-Oxygenation of Anti-Tubercular Agent Ethionamide by Peracetic Acid
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The kinetics and mechanism of the oxidation of the important antitubercular agent, ethionamide, ETA (2-ethylthioisonicotinamide), by peracetic acid (PAA) have been studied. It is effectively a biphasic reaction with an initial rapid first phase of the reaction which is over in about 5 s and a second slower phase of the reaction which can run up to an hour. The first phase involves the addition of a single oxygen atom to ethionamide to form the S-oxide. The second phase involves further oxidation of the S-oxide to desulfurization of ETA to give 2-ethylisonicotinamide. In contrast to the stability of most organosulfur compounds, the S-oxide of ETA is relatively stable and can be isolated. In conditions of excess ETA, the stoichiometry of the reaction was strictly 1:1: CH3CO3H + Et(C5H4)C(=S)NH2 → CH3CO2H + Et(C5H4)C(=NH)SOH. In this oxidation, it was apparent that only the sulfur center was the reactive site. Though ETA was ultimately desulfurized, only the S-oxide was stable. Electrospray ionization (ESI) spectral analysis did not detect any substantial formation of the sulfinic and sulfonic acids. This suggests that cleavage of the carbon-sulfur bond occurs at the sulfenic acid stage, resulting in the formation of an unstable sulfur species that can react further to form more stable sulfur species. In this oxidation, no sulfate formation was observed. ESI spectral analysis data showed a final sulfur species in the form of a dimeric sulfur monoxide species, H3S2O2. We derived a bimolecular rate constant for the formation of the S-oxide of (3.08 ± 0.72) × 102 M-1 s-1. Oxidation of the S-oxide further to give 2-ethylisonicotinamide gave zero order kinetics.
- Chipiso, Kudzanai,Logan, Isabelle E.,Eskew, Matthew W.,Omondi, Benard,Simoyi, Reuben H.
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- Efficient analoging around ethionamide to explore thioamides bioactivation pathways triggered by boosters in Mycobacterium tuberculosis
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Ethionamide is a key antibiotic prodrug of the second-line chemotherapy regimen to treat tuberculosis. It targets the biosynthesis of mycolic acids thanks to a mycobacterial bioactivation carried out by the Baeyer-Villiger monooxygenase EthA, under the control of a transcriptional repressor called EthR. Recently, the drug-like molecule SMARt-420, which triggers a new transcriptional regulator called EthR2, allowed the derepression a cryptic alternative bioactivation pathway of ethionamide. In order to study the bioactivation of a collection of thioisonicotinamides through the two bioactivation pathways, we developed a new two-step chemical pathway that led to the efficient synthesis of eighteen ethionamide analogues. Measurements of the antimycobacterial activity of these derivatives, used alone and in combination with boosters BDM41906 or SMARt-420, suggest that the two different bioactivation pathways proceed via the same mechanism, which implies the formation of similar metabolites. In addition, an electrochemical study of the aliphatic thioisonicotinamide analogues was undertaken to see whether their oxidation potential correlates with their antitubercular activity measured in the presence or in the absence of the two boosters.
- Prieri, Marion,Frita, Rosangela,Probst, Nicolas,Sournia-Saquet, Alix,Bourotte, Marilyne,Déprez, Benoit,Baulard, Alain R.,Willand, Nicolas
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- A pyridine amide synthetic method of compound
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The invention discloses a method for synthesizing a pyridine-amide compound. The method comprises the steps of carrying out hydrolysis on a pyridine cyanogen compound shown by a formula II as a starting material in water as a solvent in the presence of an ETS-10 molecular sieve as a catalyst, heating to 100-150 DEG C, reacting until the reaction, which is tracked and detected by virtue of TLC (Thin-Layer Chromatography), is completed and carrying out post-treatment on the reaction solution to obtain the pyridine-amide compound represented by the formula I. According to the method disclosed by the invention, the ETS-10 molecular sieve is taken as a catalyst to carry out hydrolysis on pyridine cyanogen to obtain a single pyridine-amide product, the conversion rate is 100%, the yield is above 95% and the catalyst can be repeatedly used for at least 5 times.
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Paragraph 0046; 0047
(2019/02/02)
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- Ethionamide biomimetic activation and an unprecedented mechanism for its conversion into active and non-active metabolites
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Ethionamide (ETH), a second-line anti-tubercular drug that is regaining a lot of interest due to the increasing cases of drug-resistant tuberculosis, is a pro-drug that requires an enzymatic activation step to become active and to exert its therapeutic effect. The enzyme responsible for ETH bioactivation in Mycobacterium tuberculosis is a monooxygenase (EthA) that uses flavin adenine dinucleotide (FAD) as a cofactor and is NADPH- and O2-dependant to exert its catalytic activity. In this work, we investigated the activation of ETH by various oxygen-donor oxidants and the first biomimetic ETH activation methods were developed (KHSO5, H2O2, and m-CPBA). These simple oxidative systems, in the presence of ETH and NAD+, allowed the production of short-lived radical species and the first non-enzymatic formation of active and non-active ETH metabolites. The intermediates and the final compounds of the activation pathway were well characterized. Based on these results, we postulated a consistent mechanism for ETH activation, not involving sulfinic acid as a precursor of the iminoyl radical, as proposed so far, but putting forward a novel reactivity for the S-oxide ethionamide intermediate. We proposed that ETH is first oxidized into S-oxide ethionamide, which then behaves as a ketene-like compound via a formal [2 + 2] cycloaddition reaction with peroxide to give a dioxetane intermediate. This unstable 4-membered intermediate in equilibrium with its open tautomeric form decomposes through different pathways, which would explain the formation of the iminoyl radical and also that of different metabolites observed for ETH oxidation, including the ETH-NAD active adduct. The elucidation of this unprecedented ETH activation mechanism was supported by the application of isotopic labelling experiments.
- Laborde, Julie,Deraeve, Céline,Duhayon, Carine,Pratviel, Geneviève,Bernardes-Génisson, Vania
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p. 8848 - 8858
(2016/10/03)
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- Acid-Free Silver-Catalyzed Cross-Dehydrogenative Carbamoylation of Pyridines with Formamides
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Primary pyridylcarboxamides are prevalent parent structures in bioactive molecules and have the apparent advantages over N-protected derivatives as synthetic building blocks. However, no practical methods have been developed for direct synthesis of this compound class from unfunctionalized pyridines. We herein present a general, safe, concise, acid-free, and highly selective method for the C2-carbamoylation of pyridines with unprotected formamide and N-methyl formamide through the cleavage of two C-H bonds.
- Han, Wei,Jin, Fengli,Zhao, Qian,Du, Hongyan,Yao, Lifang
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supporting information
p. 1854 - 1859
(2016/07/16)
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