Reaktion von Brenztraubensäure mit o-Diaminen, 3. Mitt.: Synthesen von 2-(α-Keto-alkyl)-benzimidazolen

Zellner, H.; Zellner, Gertrud; Köppl, F.; Dirnberger, J.

doi:10.1007/bf00901370

Cited by 5 publications

(7 citation statements)

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“…One notable exception is hydrazone 4 d , which we were unable to isolate. To expand the library of compounds, hydrazone 2 f was treated with aldehydes or corresponding synthetic equivalents (3‐aminopropanal diethyl acetal, crotonaldehyde, racemic glyceraldehyde and glycolaldehyde dimer) to furnish hydrazones 5 a – 5 d . Reaction of 2 f with acetone or pyruvic acid afforded hydrazones 6 a and 6 b .…”

Section: Resultssupporting

confidence: 80%

Hydrazo‐CEST: Hydrazone‐Dependent Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agents

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Suchý

Truong

et al. 2018

Chemistry A European J

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The rapid formation of hydrazones under physiological conditions was exploited for the detection of aldehydes through chemical exchange saturation transfer magnetic resonance imaging (CEST-MRI). A metal-free, diamagnetic contrast agent derived from N-amino anthranilic acid was introduced, which selectively "turned-on" upon hydrazone formation through an effect termed Hydrazo-CEST. While the hydrazine form of the probe produced no CEST-MRI signal enhancement, the formation of the aryl hydrazone resulted in >20 % intensity decrease in the bulk water signal through the CEST effect, as measured by 300 MHz H NMR, 3 T and 7 T MRI. Both the electronic contributions of the N-amino anthranilate and the aldehyde binding partner were shown to directly impact the exchange rate of the proton on the ring-proximal nitrogen, and thus the imaging signal. Additionally, the presence of the carboxylic acid moiety ortho to the hydrazine was necessary not only for contrast production, but also for rapid hydrazone formation and prolonged hydrazone product stability under physiological conditions. This work provided the first example of an MRI-based contrast agent capable of a "turn on" response upon reaction with bioactive aldehydes, and outlined both the structural and electronic requirements to expand on Hydrazo-CEST, a novel, hydrazone-dependent subtype of diamagnetic CEST-MRI.

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Section: Resultssupporting

confidence: 80%

Hydrazo‐CEST: Hydrazone‐Dependent Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agents

Dang

Suchý

Truong

et al. 2018

Chemistry A European J

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“…Similar to what was proposed by O'Sullivan in 1963 [21] and Dinbeger in 1967, [88] Ishii and co-workers in 1990 represented another route for the synthesis of 2-aroylbenzimidazole 153 in 76.5% yield, through the oxidation of 2-(αhydroxybenzyl)benzimidazoles 158 in acetone (Scheme 70). [89] Furthermore, Dupy and co-workers employed the same route using KMnO 4 or neutral alumina as oxidizing agent instead of K 2 Cr 2 O 7 , [21] or SeO 2 , [88] or MnO 2 , [89] for the synthesis of 2-ketoaryl(alkyl)benzimidazole 160 from 1-alkyl/aralkyl-2-(α-hydroxyalkyl/aryl)benzimidazoles 159 under solvent free conditions. In this study, the 1-(1H-benzo [d]imidazol-2-yl)-3-phenylpropan-1-one derivatives 163 were synthesized through the reaction of 161 with benzaldehydes 162 using NaOH as base (Scheme 71).…”

Section: Synthesis Of 2-keto Annulated Imidazolessupporting

confidence: 52%

“…Their method relied on the condensation of 2‐hydroxy‐3‐phenylacrylic acid 155 with o ‐phenlenediamine 154 under reflux conditions in ethanol to afford the 1‐(1 H ‐benzo[d]imidazol‐2‐yl)‐2‐phenylethanol 156 (Scheme 69). [88] Then, the compounds 156 were oxidized using SeO 2 in refluxed ethanol and acetic acid for 60 h to give the final products 1‐(1 H ‐benzo[d]imidazol‐2‐yl)‐2‐phenylethanone 157 .…”

Section: Synthesis Of 2‐keto Annulated Imidazolesmentioning

confidence: 99%

Strategies towards the Synthesis of 2‐Ketoaryl Azole Derivatives using C‐H Functionalization Approach and 1,2‐Bis‐Nucleophile Precursors

et al. 2023

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A spectrum of compounds attached to 2‐keto aryl azole moieties are found as pivotal building blocks in medicinal chemistry and drug discovery. This is why, the collection of novel methods have been described for the synthesis of these compounds, which are of great significance among organic chemists interested towards the development of new synthetic methods in the fields of natural products, bioactive molecules and materials sciences. This review presents the important breakthrough achieved during last decade towards improvement of approaches for the synthesis of these molecules.

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“…The 2-acetyl analogues 21 and 21a of the naphtho[2,3- d ]imidazole-4,9-diones 12 and 12a (Table ), respectively, were obtained by oxidation of 2-(1-hydroxyethyl)-1 H -naphtho[2,3- d ]imidazole with an excess of potassium dichromate to afford 21 , which upon treatment with methyl iodide gave the N -methyl analogue 21a (Scheme ).…”

Section: Chemistrymentioning

confidence: 99%

“…A solution of (±)-2-(1-hydroxyethyl)-1 H -naphtho[2,3- d ]imidazole (2.00 g, 9.43 mmol) in 96% H 2 SO 4 (8.3 mL) and water (150 mL) was heated at reflux and treated with K 2 Cr 2 O 7 (8.83 g, 30 mmol). After 1 h the mixture was cooled and filtered.…”

Section: Experimental Sectionmentioning

confidence: 99%

Synthesis and Structure–Activity Relationships of Lapacho Analogues. 2. Modification of the Basic Naphtho[2,3-b]furan-4,9-dione, Redox Activation, and Suppression of Human Keratinocyte Hyperproliferation by 8-Hydroxynaphtho[2,3-b]thiophene-4,9-diones

et al. 2014

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The basic structure of linearly anellated lapacho quinones, naphtho[2,3-b]furan-4,9-dione (7), was modified in the search for novel agents against keratinocyte hyperproliferation. The synthesis and structure-activity relationships of several heterocycle-fused naphthoquinones as well as a full range of 2- and 7-substituted derivatives of one of these, 8-hydroxynaphtho[2,3-b]thiophene-4,9-dione (8a), are described. Out of a total of 71 analogues, particularly 2-thenoyl-substituted 26l, 2-nicotinoyl-substituted 26m, and 2-oxadiazole-substituted 35a compared favorably with the antipsoriatic agent anthralin. Their potency for suppression of keratinocyte hyperproliferation, which was evaluated using HaCaT cells as a model, was combined with comparably low membrane-damaging effects toward keratinocytes, as established by the release of lactate dehydrogenase activity from the cytoplasm of the cells. With respect to the mechanism of action, redox activation of lapacho quinones by one- and two-electron reduction in isolated enzymatic assays was studied, and their potential to generate superoxide was confirmed in the keratinocyte-based hyperproliferation assay.

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Reaktion von Brenztraubensäure mit o-Diaminen, 3. Mitt.: Synthesen von 2-(α-Keto-alkyl)-benzimidazolen

Cited by 5 publications

References 0 publications

Hydrazo‐CEST: Hydrazone‐Dependent Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agents

Hydrazo‐CEST: Hydrazone‐Dependent Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agents

Strategies towards the Synthesis of 2‐Ketoaryl Azole Derivatives using C‐H Functionalization Approach and 1,2‐Bis‐Nucleophile Precursors

Synthesis and Structure–Activity Relationships of Lapacho Analogues. 2. Modification of the Basic Naphtho[2,3-b]furan-4,9-dione, Redox Activation, and Suppression of Human Keratinocyte Hyperproliferation by 8-Hydroxynaphtho[2,3-b]thiophene-4,9-diones

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