A Simple Method of Synthesis of 3-Carboxy-2,2,5,5-Tetraethylpyrrolidine-1-oxyl and Preparation of Reduction-Resistant Spin Labels and Probes of Pyrrolidine Series

Stable free radicals are widely used as molecular probes and labels in various biophysical and biomedical research applications of magnetic resonance spectroscopy and imaging. Among these radicals, sterically shielded nitroxides of pyrrolidine series demonstrate the highest stability in biological systems. Here, we suggest new convenient procedure for preparation of 3-carboxy-2,2,5,5-tetraethylpyrrolidine-1-oxyl, a reduction-resistant analog of widely used carboxy-Proxyl, from cheap commercially available reagents with the yield exceeding the most optimistic literature data. Several new spin labels and probes of 2,2,5,5-tetraethylpyrrolidine-1-oxyl series were prepared and reduction of these radicals in ascorbate solutions, mice blood and tissue homogenates was studied.     

Using a comparison theorem for evaluating the stress for plane cracks in transversally isotropic media

An established thermoelastic analogy for transversally isotropic media and the Hopf principle of the maximum are used to prove a comparison theorem for estimating the stress for plane cracks of complex shape (in the place perpendicular to the plane of isotropy) in the presence of force and temperature loading. This approach makes it possible to construct simple bounding contours and provide two-sided estimates forK ₁. The effectiveness of this approach is demonstrated on specific examples. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 35, No. 7, pp. 85–94, July, 1999.     

Nitration of imidazoline-n-oxide nitroxides containing the aryl nitrone group

Nitration of 4-aryl-3-imidazoline-3-oxide nitroxyl radicals leads to 4-nitroaryl-3-imidazoline-3-oxide nitroxides via oxammonium salts formation, the nitrone group being an ortho-para orientant.     

Minimal average stresses in a medium with an inhomogeneity

S. P. Timoshenko Mechanics Institute, Academy of Sciences of the Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 29, No. 12, pp. 36–42, December, 1993.     

Synthesis of new spin probes based on aminoaryl-substituted imidazoline nitroxides

A series of new spin probes, azides and isothiocyanates, were synthesized starting from aminoaryl-substituted nitroxides which are derivatives of 3-imidazoline and 3-imidazoline-3-oxide. The new compounds were transformed to complexones, derivatives of iminodiacetic acid.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 465–468, March, 1994.     

Synthesis of nitroxyl radicals — Derivatives of 5,5-dimethoxy-3-imidazoline-3-oxide-1-oxyl from 2H-imidazole 1,3-dioxides

2H-Imidazole 1,3-dioxides containing an aldonitrone fragment in the heterocyclic ring are obtained by the oxidation of 5-unsubstituted 1-hydroxy-3-imidazoline 3-oxides. Their further oxidation by lead dioxide in methanol leads to the formation of stable nitroxyl radicals — 5,5-dimethoxy-3-imidazoline-3-oxide-1-oxyls.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2122–2126, September, 1991.