- Synthesis of new pyrrolidine nitroxide epoxides as versatile paramagnetic building blocks
-
Pyrrolidine nitroxide epoxides were synthesized by oxidation of the corresponding alkene, diene and α,β-unsaturated aldehyde with m-CPBA or H2O2 to provide new spin labels and paramagnetic synthons.
- Kálai, Tamás,Sár, Cecília P.,Jeko, József,Hideg, Kálmán
-
-
Read Online
- A CONVENIENT HIGH YIELD SYNTHESIS OF NITROXIDES
-
Appropriate secondary amines are readily converted to nitroxides by dimethyldioxirane in a rapid, convenient, and essentially quantitative process.
- Murray, Robert W.,Singh, Megh
-
-
Read Online
- Synthesis and spectral properties of polymethine-cyanine dye-nitroxide radical hybrid compounds for use as fluorescence probes to monitor reducing species and radicals
-
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.
- 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)
-
- Synthesis and structure of products of hydroxylamine acylation with 3-carboxy-2,2,5,5-tetramethylpyrrolinoxyl derivatives
-
The reaction of NH2OH with the derivatives of 2,2,5,5-tetramethylpyrrolin-1-oxyl-3-carboxylic acid in all events led to the formation of a mixture of the corresponding nitroxylhydroxamic acid with a stable O-acylhydroxylamine. The ratio between
- Sen,Shilov,Golubev
-
experimental part
p. 1189 - 1199
(2009/12/09)
-
- First synthesis of novel spin-labeled derivatives of camptothecin as potential antineoplastic agents
-
In an effort to improve the stability of labile lactone ring and water solubility of camptothecin, five novel spin-labeled camptothecin derivatives were synthesized in quantitative yield by a simple modification of the carbodiimide method using the combination of scandium triflate (Sc(OTf)3) and 4-dimethylaminopyridine (DMAP), and the in vitro pharmacokinetic determination of the lactones of representative compound 13a showed that the biological life span of their lactone forms in human and mouse plasma significantly increased when compared with their mother compound camptothecin. Also, the in vitro cytotoxicity of compounds 13a-13e against human bladder cancer T-24 showed either similar or better activity than that of the parent drug, camptothecin, and clinically available drug, irinotecan.
- Liu, Ying-Qian,Tian, Xuan,Yang, Liu,Zhan, Zong-Cheng
-
scheme or table
p. 2610 - 2614
(2009/04/11)
-
- Synthesis of nitroxide containing polyenes: two chemically modified retinals and their interaction with bacterioopsin
-
The synthesis and spectroscopic characterization of two retinal analogues is described, the paramagnetic 3-pyrrolin-1-yloxy analogue 1 and its diamagnetic equivalent, the 3-pyrroline analogue 2.Various aspects of the synthesis of the aminoxy group containing polyenes are discussed.Upon interaction with bacterioopsin, both 1 and 2 are incorporated in the protein and form a system with λmax 459 nm.Neither of the two bacteriorhodopsin analogues is photoactive.ESR spectroscopy data of the system containing 1 show that the ring part of the chromophore in the protein is rigidly fixed in orientation.
- Groesbeek, M.,Lugtenburg, J.
-
p. 403 - 409
(2007/10/03)
-
- INFLUENCE OF CHEMICAL STRUCTURE OF NITROXYL SPIN LABELS ON THEIR REDUCTION BY ASCORBIC ACID
-
The influence of structure on the reduction of nitroxyl spin labels by ascorbic acid was examined using both piperidine and pyrrolidine nitroxyls.A five-fold molar excess of ascorbic acid and pH of 7.4 were used.The nitroxyl concentration was measured by electron spin resonance spectrometry.The five-membered (pyrrolidine) nitroxyls were more stable than the six-membered derivatives.Ring substituents also influenced the reaction.The anionic derivatives were more stable than the unionized compounds which, in turn, were more stable than the amines (cations at pH 7.4).
- Couet, W. R.,Brasch, R. C.,Sosnovsky, G.,Lukszo, J.,Prakash, I.,et. al.
-
p. 1165 - 1172
(2007/10/02)
-