Polarity effects in 4-fluoro- and 4-(trifluoromethyl)prolines

• Vladimir Kubyshkin

Beilstein J. Org. Chem. 2020, 16, 1837–1852, doi:10.3762/bjoc.16.151

• rotation should not necessarily proceed from the major conformation. This is an important precaution that should be kept in mind in the analysis of the data. In model compounds, the barrier of rotation can be determined relatively accurately with the experimental methods such as EXSY NMR [94]. However, the

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• of these protons because of its non-equivalent nature. The structures of conformers 1a-1 and 1a-2 were further confirmed by 2D NMR experiments. We performed 2D exchange spectrometry (EXSY) NMR experiments to confirm that there is a change of conformation on the NMR timescale [17]. This technique

cis–trans-Amide isomerism of the 3,4-dehydroproline residue, the ‘unpuckered’ proline

• Vladimir Kubyshkin and
• Nediljko Budisa

Beilstein J. Org. Chem. 2016, 12, 589–593, doi:10.3762/bjoc.12.57

• values found in solution both indicate close conformational similarities between Dhp and Pro fragments. Finally, we identified the amide rotation rates and corresponding activation barriers by EXSY NMR (D2O, 310 K). In order to establish a proper reference system we correlated the observed activation

Thermodynamic and kinetic stabilization of divanadate in the monovanadate/divanadate equilibrium using a Zn-cyclene derivative: Towards a simple ATP synthase model

• Hanno Sell,
• Anika Gehl,
• Frank D. Sönnichsen and
• Rainer Herges

Beilstein J. Org. Chem. 2012, 8, 81–89, doi:10.3762/bjoc.8.8

• thermodynamically as shown by NMR titration. Moreover, EXSY NMR experiments reveal that the vanadate dimer is also kinetically stabilized with respect to hydrolysis by complexation with Zn-cyclene. Keywords: EXSY NMR; NMR titration; supramolecular chemistry; vanadate condensation; 51V NMR; Zn-cyclene

• condensation and hydrolysis of the involved vanadium oxo-anions was examined by 51V EXSY NMR experiments [27][28]. 51V EXSY NMR data were collected for solutions buffered with EPPS and HEPES and 1.5 mM total vanadium concentration at 25 °C. For each buffer solution, the amount of Zn-benzylcyclene 1 was varied

• ligand 1, as determined by 51V EXSY NMR experiments. Dimerization, however, is less favorable if both reacting monovanadate units are complexed with ligand 1 (ΔG30 = −13.1 kJ mol−1) compared to the reaction of a complexed vanadate with a free monovanadate (ΔG20 = −14.8 kJ mol−1). For the design of an