Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• -Semiquinones are often used as convenient spin labels to determine the spatial arrangement of ligands and to monitor the processes in the coordination sphere of metal ions in real time [42][43][44][45][46]. The spin density distribution and thus the hyperfine coupling constants for the magnetic nuclei at the

Unexpected one-pot formation of the 1H-6a,8a-epiminotricyclopenta[a,c,e][8]annulene system from cyclopentanone, ammonia and dimethyl fumarate. Synthesis of highly strained polycyclic nitroxide and EPR study

• Sergey A. Dobrynin,
• Igor A. Kirilyuk,
• Yuri V. Gatilov,
• Andrey A. Kuzhelev,
• Olesya A. Krumkacheva,
• Matvey V. Fedin,
• Michael K. Bowman and
• Elena G. Bagryanskaya

Beilstein J. Org. Chem. 2019, 15, 2664–2670, doi:10.3762/bjoc.15.259

• cyclopentanone and ammonia. The polycyclic amine product was then converted into a sterically shielded polycyclic nitroxide. Sterically hindered nitroxides have high chemical stability [5] and can be used as spin labels to study biopolymers in cells [6]. The introduction of spirocyclic moieties has a smaller

• effect on the reduction rates of nitroxides than does the introduction of linear alkyl substituents. However, spirocyclic nitroxides may have much longer spin relaxation times at 70–150 K which make them attractive agents for spin labeling [7][8][9]. Sterically hindered nitroxides can be used as spin

• labels for measurements at room temperature [10]. In this paper we examined the properties of this new nitroxide, in particular, the electron spin relaxation at different temperatures in water/glycerol solution. Results and Discussion Synthesis Polycyclic amine A mixture cyclopentanone, dimethyl fumarate

Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

• Ayato Yamada,
• Manabu Abe,
• Yoshinobu Nishimura,
• Shoji Ishizaka,
• Masashi Namba,
• Taku Nakashima,
• Kiyofumi Shimoji and
• Noboru Hattori

Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

• sciences. These applications include spin-labels [5][6][7], fluorophore-nitroxide probes [8], contrast agents in magnetic resonance imaging (MRI) [9], polarization transfer agents for nuclear magnetic resonance (NMR) [10][11][12][13], and radical batteries [14][15]. Furthermore, the efficient synthesis of

Phosphoramidite building blocks with protected nitroxides for the synthesis of spin-labeled DNA and RNA

• Timo Weinrich,
• Eva A. Jaumann,
• Ute M. Scheffer,
• Thomas F. Prisner and
• Michael W. Göbel

Beilstein J. Org. Chem. 2018, 14, 1563–1569, doi:10.3762/bjoc.14.133

• , Max-von-Laue-Str. 7, D-60438 Frankfurt am Main, Germany 10.3762/bjoc.14.133 Abstract TEMPO spin labels protected with 2-nitrobenzyloxymethyl groups were attached to the amino residues of three different nucleosides: deoxycytidine, deoxyadenosine, and adenosine. The corresponding phosphoramidites

• oligonucleotides by phosphoramidite building blocks [27][28][29][30][31][32][33][34][35][36][37][38][39][40]. However, some degradation of the spin labels inevitably will occur. Nitroxide labeled DNA strands of the general structures 2 and 4 have been prepared by this way [30][34][37]. In recent years, we have

• hydroxylamines spontaneously reacted with air to form the nitroxide radicals in high yield [43]. Although the rigid spin labels introduced by Sigurdsson [31][32][33], Hopkins [27][29] and Engels [20][21] are generally considered advantageous for EPR studies, TEMPO-modified RNAs according to structures 1 and 3

TEMPO-derived spin labels linked to the nucleobases adenine and cytosine for probing local structural perturbations in DNA by EPR spectroscopy

• Dnyaneshwar B. Gophane and
• Snorri Th. Sigurdsson

Beilstein J. Org. Chem. 2015, 11, 219–227, doi:10.3762/bjoc.11.24

• Dnyaneshwar B. Gophane Snorri Th. Sigurdsson University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland 10.3762/bjoc.11.24 Abstract Three 2´-deoxynucleosides containing semi-flexible spin labels, namely TA, UA and UC, were prepared and incorporated into

• formation of TAH+•C and TAH+•G, in which protonation of N1 of A allows the formation of an additional hydrogen bond to N3 of C and N7 of G, respectively, with G in a syn-conformation. The urea-based spin labels UA and UC were more mobile than TA, but still showed a minor variation in their EPR spectra when

• biologically relevant conditions through the determination of intermediate to long-range distances [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. EPR spectroscopy can also give information about the relative orientation of two rigid spin labels [31][32][33][34][35]. Small angle X-ray

A new building block for DNA network formation by self-assembly and polymerase chain reaction

• Holger Bußkamp,
• Sascha Keller,
• Marta Robotta,
• Malte Drescher and
• Andreas Marx

Beilstein J. Org. Chem. 2014, 10, 1037–1046, doi:10.3762/bjoc.10.104

• containing spin labels covalently bound to DNA. All EPR spectra were measured in X-band (9.5 GHz) at room temperature in solution and are shown as first derivatives. For later comparison, spin-labeled TTP analogue dT*TP (Figure 5D) was measured and results to EPR spectra with three narrow lines indicating a

• natural dNTPs. We obtained spectra showing that the spin-labeled nucleotide was indeed incorporated into the DNA (Figure 5B,C). All spectra were quantitatively analyzed by spectral line shape simulations. Thereby, the dynamics of the nitroxide spin-labels are reflected in rotational correlation times τc

• indicated network formation in solution and suggests rather rigid DNA networks. A more detailed analysis of the spectrum results in two components; the first component (contributing 8%) features a rotational correlation time (τc = 0.17 ± 0.02 ns) almost identical to τc of spin labels in linear DNA (τc