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

• hindered nitroxide, we investigated its electron spin relaxation properties in water/glycerol solution which is the solvent of choice for biomolecular distance measurements by PELDOR/DEER. If the rotation of the radical is prevented, the primary relaxation mechanisms are (i) modulation of the 14N hyperfine

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition

• Yulia V. Khoroshunova,
• Denis A. Morozov,
• Andrey I. Taratayko,
• Polina D. Gladkikh,
• Yuri I. Glazachev and
• Igor A. Kirilyuk

Beilstein J. Org. Chem. 2019, 15, 2036–2042, doi:10.3762/bjoc.15.200

• effect may be useful for structural studies by means of PELDOR or DQC [5]. We recently reported the synthesis of sterically shielded pyrrolidine nitroxide 1 via a stereospecific consecutive assembly of two spiro-(2-hydroxymethyl)cyclopentane moieties. These procedures included the addition of pent-4

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

• resulting spin-labeled palindromic duplexes could be directly investigated by PELDOR spectroscopy without further purification steps. Spin–spin distances measured by PELDOR correspond well to the values obtained from molecular models. Keywords: EPR; oligonucleotide; PELDOR; photolabile protection; TEMPO

• have been successfully used in PELDOR experiments to determine the distance between two spins [8][25][43]. The apparent usefulness of such building blocks has prompted us in the present study to extend the protection strategy from amidite 6 to its DNA analog 5 and to adenosine derivatives 7 and 8

• reduction products 22d–27d. Hydrolytic degradation of the oligonucleotides was not observed. For successful PELDOR experiments the quality of spin labeled samples is essential. We have shown previously that RNA strands synthesized from amidite 6 are ready for PELDOR studies directly after photochemical