Synthesis, structure, and X-band (9.5 GHz) EPR characterization of the new series of pH-sensitive spin probes: N,N-disubstituted 4-amino-2,2,5,5-tetramethyl-3-imidazoline 1-oxyls

Synthesis, structure, and X-band (9.5 GHz) EPR characterization of the new series of pH-sensitive spin probes: N,N-disubstituted 4-amino-2,2,5,5-tetramethyl-3-imidazoline 1-oxyls Full article

Journal

Journal of Organic Chemistry
ISSN: 0022-3263

Output data

Year: 2005, Volume: 70, Number: 24, Pages: 9702-9711 Pages count : 10 DOI: 10.1021/jo0510890

Authors

Voinov MA ¹ , Polienko JF ^2,3 , Schanding T ⁴ , Bobko AA ⁵ , Khramtsov VV ^5,6 , Gatilov YV ² , Rybalova TV ² , Smirnov AI ¹ , Grigor'ev IA ^2,3

Affiliations

1	(Данные Web of science) N Carolina State Univ, Dept Chem, Raleigh, NC 27695 USA
2	(Данные Web of science) Novosibirsk Organ Chem Inst, Novosibirsk 630090, Russia
3	(Данные Web of science) Novosibirsk State Univ, Novosibirsk 630090, Russia
4	(Данные Web of science) Univ Kaiserslautern, Fachbereich Chem, D-67663 Kaiserslautern, Germany
5	(Данные Web of science) Russian Acad Sci, Inst Chem Kinet & Combust, Novosibirsk 630090, Russia
6	(Данные Web of science) Ohio State Univ, Dorothy M Davis Heart & Lung Res Inst, Columbus, OH 43210 USA

An approach to the synthesis of new imidazoline nitroxides bearing an N',N'-disubstituted amidine group is reported. The approach is based on the alkylation of diamagnetic 4-R-amino-1,2,2,5,5pentamethyl-3-imidazolines with bromoacetic acid ethyl ester; the products of alkylation are further oxidized to the corresponding nitroxides. The approach allows a variety of functional groups to be introduced into the nitroxide molecule structure. Alkylation with bromoacetic acid ethyl ester was found to proceed with high regioselectivity and afford the products of exo-alkylation. The regiochemical assignment is made on the basis of C-13 NMR spectra and confirmed by X-ray diffraction study. All of the nitroxides synthesized here were shown to have pH-dependent EPR spectra with pK(a) ranging from 3.5 to 6.2. For nitroxides 13 bearing the carboxylic group remote to the nitroxide moiety, the changes in isotropic magnetic parameters of EPR spectra due to reversible deprotonation of the carboxylic group were found to be small. For these nitroxides, we demonstrate an alternative approach for pKa determination that is based on measuring the peak-to-peak line width of the EPR spectrum in the presence of the paramagnetic broadening agent potassium ferricyanide. The partition coefficients of nitroxides in octanol/H2O and octanol/phosphate buffer solution mixtures were measured to reveal a range of their lipophilicities.

Voinov M. , Polienko J. , Schanding T. , Bobko A. , Khramtsov V. , Gatilov Y. , Rybalova T. , Smirnov A. , Grigor'ev I.
Synthesis, structure, and X-band (9.5 GHz) EPR characterization of the new series of pH-sensitive spin probes: N,N-disubstituted 4-amino-2,2,5,5-tetramethyl-3-imidazoline 1-oxyls
Journal of Organic Chemistry. 2005. V.70. N24. P.9702-9711. DOI: 10.1021/jo0510890 WOS Scopus РИНЦ OpenAlex

Published print:

Nov 1, 2005

Web of science:	WOS:000233539200005
Scopus:	2-s2.0-28144444935
Elibrary:	13498104
OpenAlex:	W2007728586

DB	Citing
Web of science	18
Scopus	23
Elibrary	23
OpenAlex	25