46147-12-0Relevant articles and documents
Synthesis of Isoselenocyanates
Zakrzewski, Jerzy,Huras, Bogumi?a,Kie?czewska, Anna
, p. 85 - 96 (2015/12/26)
Isoselenocyanates were synthesized by two methods under phase-transfer conditions (50% aq NaOH, CH2Cl2, Aliquat 336); the first started from isocyanides and selenium and gave isoselenocyanates in 61-89% yields, while the second started from amines and used chloroform and selenium, by applying sequentially the Hofmann isonitrile synthesis and the addition of selenium, in 4-70% yields.
Synthesis and spectral properties of polymethine-cyanine dye-nitroxide radical hybrid compounds for use as fluorescence probes to monitor reducing species and radicals
Sato, Shingo,Tsunoda, Minoru,Suzuki, Minoru,Kutsuna, Masahiro,Takido-uchi, Kiyomi,Shindo, Mitsuru,Mizuguchi, Hitoshi,Obara, Heitaro,Ohya, Hiroaki
experimental part, p. 2030 - 2039 (2009/03/12)
Various hybrid compounds comprised of two types of nitroxide radicals and either a pentamethine (Cy5) or trimethine cyanine (Cy3) were synthesized. The nitroxide radicals were linked either via an ester-bond to one or two N-alkyl carboxyl-terminated groups of Cy5, or via two amido-bonds (aminocarbonyl or carbonylamino group) to the 5-position of the indolenine moieties of Cy5 and Cy3. Changes in fluorescence and ESR intensities of the hybrid compounds were measured before and after addition of Na ascorbate in PBS (pH 7.0) to reduce the radicals. Among the hybrid compounds synthesized, those that linked the nitroxide radicals via an aminocarbonyl residue at the 5-position of the indolenine moieties on Cy5 and Cy3 exhibited a 1.8- and 5.1-fold increase in fluorescence intensity with the reduction of the nitroxide segment by the addition of Na ascorbate, respectively. In contrast, fluorescence intensity was not enhanced in the other hybrid compounds. Thus, the hybrid compounds which exhibited an increase in fluorescent intensity with radical reduction can be used in the quantitative measurement of reducing species such as Fe2+ and ascorbic acid, and hydroxyl radicals. Because these hybrid compounds have the advantage of fluorescing at longer wavelengths-661 (Cy5) or 568 (Cy3) nm, respectively, they can be used to measure radical-reducing species or radicals either in solution or in vivo.
The role of oxoammonium cation in the SOD-mimic activity of cyclic nitroxides
Goldstein, Sara,Merenyi, Gabor,Russo, Angelo,Samuni, Amram
, p. 789 - 795 (2007/10/03)
Cyclic nitroxides (RNO·) mimic the activity of superoxide dismutase (SOD) and demonstrate antioxidant properties in numerous in vitro and in vivo models. Their broad antioxidant activity may involve the participation of their reduced and oxidized forms, that is, hydroxylamine (RNO-H) and oxoammonium cation (RNO+). To examine this possibility we studied the reactions of RNO· and RNO+ with HO2·/O2·- and with several reductants by pulse radiolysis and rapid-mixing stopped-flow techniques. The oxoammonium cations were generated by electrochemical and radiolytic oxidation of 2,2,6,6-tetramethylpiperidinoxyl (TPO) and 3-carbamoyl-2,2,5,5-tetramethylpyrrolidinoxyl (3-CP). The rate constant for the reaction of RNO· with HO2· to form RNO+ was determined to be (1.2 ± 0.1) × 108 for TPO and (1.3 ± 0.1) × 106 M-1 s-1 for 3-CP. The kinetics results demonstrate that the reaction of RNO· with HO2· proceeds via an inner-sphere electron-transfer mechanism. The rate constant for the reaction of RNO· with O2·- is lower than 1 x 103 M-1 s-1. The rate constant for the reaction of RNO+ with O2·- was determined to be (3.4 ± 0.2) × 109 for TPO+ and (5.0 ± 0.2) × 109 M-1 s-1 for 3-CP+. Hence, both nitroxides catalyze the dismutation of superoxide through the RNO·/RNO+ redox couple, and the dependence of the catalytic rate constant, kcat, on pH displayed a bell-shaped curve having a maximum around pH 4. The oxoammonium cation oxidized ferrocyanide and HO2- by a one-electron transfer, whereas the oxidation of methanol, formate, and NADH proceeded through a two-electron-transfer reaction. The redox potential of RNO·/RNO+ couple was calculated to be 0.75 and 0.89 V for 3-CP and TPO, respectively. The elucidated mechanism provides a clearer insight into the biological antioxidant properties of cyclic nitroxides that should permit design of even more effective antioxidants.
