The Synthesis of Amidine Derivatives of Imidazoline Nitroxides - A New Series of pH-Sensitive Spin Probes and Labels

Balakirev, Maxim Y.; Khramtsov, Valery V.; Berezina, T. A.; Martin, Valérie; Volodarsky, L. B.

doi:10.1055/s-1992-26343

Cited by 19 publications

(14 citation statements)

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“…IR spectrum, ν, cm -1 : 1759 (C=O); 1690 (C=N); 1577 (COO - Titration of Amidine Acid 6 Using EPR Spectroscopy (9.5 GHz). The titration is carried out using a published method [24]. A solution of the amidine acid was prepared in 10 mM buffered sodium phosphate solution with a nitroxyl radical concentration of approximately 0.1 mM.…”

Section: Reactions Of 1-ethoxycarbonylmethyl-5577-tetramethyl-2-oxmentioning

confidence: 99%

Synthesis of N'-substituted amidines through the cleavage an oxadiazolone heterocycle by weakly basic nucleophiles. Effect of the nature of the nucleophile and of the nucleophile/substrate molar ratio

Polienko

Grigor’yev

Voinov

2009

Chem Heterocycl Comp

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NaNO 2 has been studied. It was shown for the first time that, as in the case of NaOH and MeONa, the reaction occurs with opening of the oxadiazolone ring to form exo-N-substituted amidines. It was shown that the weakly basic nucleophiles readily react with substrates which contain a substituent sensitive to attack by such nucleophiles as NaOH or MeONa. The effect of the nature of the nucleophiles on the reaction course for opening of the oxadiazolone ring was also studied. It was found that the reactivity of the nucleophiles in DMSO changes in the series F -> CN -> N 3 ->NO 2 -> Cl -> Br -and qualitatively correlates with their basicities in this solvent. Examination of the effect of the ratio of the reagents on the degree of conversion of the starting oxadiazolone has shown that a quantity of nucleophiles less than one equivalent also allowed the cleavage reaction of the oxadiazolone heterocycle to go to completion through just increasing the reaction time. The experimental data obtained lends support to the proposed reaction scheme.The 1,3-dipolar cycloaddition reaction of isocyanates to aldonitrones is one of the most efficient methods of synthesizing heterocyclic compounds. The cycloadducts formed (1,2,4-oxadiazol-5-one derivatives) are characterized by high stability and are used to capture unstable nitrones in order to identify them in an _______ * Dedicated to Academician B. A. Trofimov in his 70 th jubilee.

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Section: Reactions Of 1-ethoxycarbonylmethyl-5577-tetramethyl-2-oxmentioning

confidence: 99%

Synthesis of N'-substituted amidines through the cleavage an oxadiazolone heterocycle by weakly basic nucleophiles. Effect of the nature of the nucleophile and of the nucleophile/substrate molar ratio

Polienko

Grigor’yev

Voinov

2009

Chem Heterocycl Comp

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“…However, the known methods of synthesis [4][5][6] permit only a limited variation in structure of this type of nitroxide. Here we report a new approach to the synthesis of 4-dialkylamino-2,5-dihydro-1H-imidazol-1-oxyls via direct introduction of a secondary or tertiary amino group to the heterocycle by nucleophilic substitution of a cyano group in 4H-imidazole-5-carbonitrile 3-oxides (Scheme 1).…”

Section: Figurementioning

confidence: 99%

“…This was performed similarly to the procedure described. 6 The nitroxides were dissolved in phosphate buffer (1 mM; pH 6.03) to reach a final concentration of the nitroxide of ca. 0.1 mM.…”

Section: Titration Of the Nitroxides 7a-gmentioning

confidence: 99%

Grignard Reagent Addition to5-Alkylamino-4H-Imidazole 3-Oxides: Synthesisof New pH-Sensitive Spin Probes

Kirilyuk¹,

Shevelev²,

Morozov³

et al. 2003

Synthesis

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4,4-Dimethyl-4H-imidazole-5-carbaldehyde oxime 3oxides 4 were prepared by oxidation and nitrosation of 4,5,5-trimethyl-2,5-dihydro-1H-imidazol-1-ols. The oximes 4 were converted to 5-cyano derivatives; the latter react with primary or secondary amines to form 5-(di)alkylamino-4H-imidazole 3-oxides 6. Treatment of 6 with AlkMgX and subsequent oxidation yielded stable nitroxides 4-(di)alkylamino-2,5-dihydroimidazole-1-oxyls 7, the pHsensitive spin probes.

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“…Synthesis of the biradicals (I) and (III) was described in [12] and [13], respectively. Biradical (II) was synthesized according to the following scheme:…”

Section: Synthesis Of the Biradicalsmentioning

confidence: 99%

“…Cycloadduct (IV) and aldonitrone (V) were prepared according to procedures described in [12] and [14], respectively. 1,3-Bis(4,4,6,6-tetramethyl-5-oxyl-2-oxoperhydroimidazo[ 1 ,5-b]oxadiazole-1 ,2,4-3-yl)-6-methylbenzene (VI) was synthesized as follows.…”

Section: Synthesis Of the Biradicalsmentioning

confidence: 99%

Imidazoline biradical spin labels with EPR spectral sensitivity to the local concentration of protons

et al. 1998

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EPR spectral sensitivity of the three biradicals of imidazoline and imidazolidine types to the local concentration of protons (pH) in aqueous solutions has been studied. Significant increase in g-factor (Ag 0.0002) and decrease in hyperfine interaction constant (AaN = 0.8-1.2 G) upon the protonation of atom N-3 of the radical heterocycle were observed. The pH dependence of a N and gfactor is described by conventional titration curve with one or two pK values. The latter case was explained by nonindependent protonation of two monoradical fragments closely located in the biradical structure. EPR spectra of protonated and deprotonated forms of the biradicals have significantly different intensities of "biradical" components, Ib, reflecting changes in spin exchange interaction. It has been found that activation energy of spin exchange, Ea, estimated from temperature dependence of Ib in glycerol/water solution is lower for the biradical conformation with larger I b . This is in agreement with main contribution of direct collisions of monoradical fragments in spin exchange interaction so larger value of Ib corresponds to the conformation with less spatial restrictions for the motion of monoradical fragments (lower Ea). The potential use of the pH-sensitive biradicals as spin labels is discussed.

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The Synthesis of Amidine Derivatives of Imidazoline Nitroxides - A New Series of pH-Sensitive Spin Probes and Labels

Cited by 19 publications

References 0 publications

Synthesis of N'-substituted amidines through the cleavage an oxadiazolone heterocycle by weakly basic nucleophiles. Effect of the nature of the nucleophile and of the nucleophile/substrate molar ratio

Synthesis of N'-substituted amidines through the cleavage an oxadiazolone heterocycle by weakly basic nucleophiles. Effect of the nature of the nucleophile and of the nucleophile/substrate molar ratio

Grignard Reagent Addition to5-Alkylamino-4H-Imidazole 3-Oxides: Synthesisof New pH-Sensitive Spin Probes

Imidazoline biradical spin labels with EPR spectral sensitivity to the local concentration of protons

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