Triphenylpyridinium derivatives of α-amino-acids and a dipeptide

Katritzky, Alan R.; Grzeskowiak, Nicholas E.; Eweiss, N. F.; Elsherbini, E. A.

doi:10.1039/p19830000497

Cited by 11 publications

(4 citation statements)

References 2 publications

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“…The compounds 2,4,6-triphenylthiopyrylium perchlorate ( 9 ) and 2,4,6-triphenyl-1-methylpyridinium perchlorate ( 10 ) were both prepared from 2,4,6-triphenylpyrylium perchlorate as described in ref . To obtain 9 , 2,4,6-triphenylpyrylium perchlorate was treated with sodium sulfide, while in the case of 10 it was allowed to react with glycine . The neutral radicals 11 − 14 were generated electrochemically during the cyclic voltammetric scan from the pertinent cations 7 − 10 , i.e., the redox features of 11 − 14 could be characterized by studying the second redox waves of 7 − 10 .…”

Section: Methodsmentioning

confidence: 99%

On the Nature of Solvent Effects on Redox Properties

et al. 2004

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The one-electron reduction potentials of six radical cations, four cations, and four neutral radicals in tetrahydrofuran, dichloromethane, dimethyl sulfoxide, N-methyl-2-pyrrolidinone, N,N-dimethylformamide, acetonitrile, methanol, ethanol, 2-propanol, acetone, formamide, and 1,1,1,3,3,3-hexafluoropropan-2-ol have been measured by cyclic voltammetry. For 10 of the redox couples, the redox process was reversible in all solvents. These results have been used to evaluate solvent effects by means of the Kamlet-Taft relationship. The relative importance of the solvent parameters R, β, π*, and δ H is 54.9, 9.6, 15.5 and 20.0%, respectively, for the radical cation displaying the strongest solvent dependence. In addition, we have studied the entropy contribution to some of the observed solvent effects by measuring the redox potentials as a function of temperature. The absolute value of the entropy appears to increase with increasing hydrogen bond donor ability of the solvent. The variation in entropy indicates that specific solvation is of main importance when considering solvent effects on redox properties.

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Section: Methodsmentioning

confidence: 99%

On the Nature of Solvent Effects on Redox Properties

et al. 2004

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“…Accordingly, the isoquinoline core in 1 and 2 is likely to be derived by initial Schiff-base formation between the amino group of leucine or isoleucine with one of the carbonyl groups of A . Subsequent ring closure and dehydration reactions would produce a delocalized isoquinolinium intermediate. , The positive charge of the nitrogen atom could favor a delocalized ylide structure via base-catalyzed/enzymatic abstraction of the α-proton of the amino acid residue, thus facilitating partial racemization at this position. Successive hydration and oxidation reactions would then result in the formation of the isoquinolinone intermediate B bearing both the l - and d -form of the respective amino acid.…”

Section: Resultsmentioning

confidence: 99%

Chaetolines A and B, Pyrano[3,2-f]isoquinoline Alkaloids from Cultivation of Chaetomium sp. in the Presence of Autoclaved Pseudomonas aeruginosa

et al. 2018

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The first members of a new alkaloid class, chaetolines A (1) and B (2), which feature a pyrano[3,2f ]isoquinoline core structure, were obtained from a crude extract of the fungal endophyte Chaetomium sp. after cultivation in the presence of autoclaved Pseudomonas aeruginosa. The structures of the new compounds, including the absolute configuration of the major stereoisomer, were determined through detailed analysis of HRESIMS, 1D/2D NMR, and calculation of ECD data. The possible biosynthetic origin of the unprecedented scaffold of 1 and 2 is proposed. The current study provides further evidence for mixed fermentation as a powerful tool to induce the accumulation of cryptic fungal natural products even in the absence of viable bacterial cells.

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“…Katritzky pyridinium salts, [25][26][27] easily prepared in one step by the condensation of pyrylium salts with primary amines, are air and moisture-stable and convenient for purification via filtration. Recently, Katritzky salts have been widely investigated as precursors for the generation of alkyl radical species and the subsequent cross-coupling reactions.…”

Section: Introductionmentioning

confidence: 99%