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

• compounds 5 and 6 follow generally similar chiral bias to 3 and 4. The pKa data for the free amino acids shows that there is an identical reduction of the pKa values from fluorination (Figure 10B and C). It was then found that neither the side-chain conformation markers (J coupling at 2-CH) nor the trans

• examined in this study. Design of the model system. Propagation of the C4-conformation into the values of the J coupling in the C2H–C3H2 fragments. Preferred side-chain conformations according to the multiplicity data. A) The basicity reduction from the introduction of the dipoles reflects the preferred

Influence of per-O-sulfation upon the conformational behaviour of common furanosides

• Alexey G. Gerbst,
• Vadim B. Krylov,
• Dmitry A. Argunov,
• Maksim I. Petruk,
• Arsenii S. Solovev,
• Andrey S. Dmitrenok and
• Nikolay E. Nifantiev

Beilstein J. Org. Chem. 2019, 15, 685–694, doi:10.3762/bjoc.15.63

• ). NMR data of furanosides 1–3 and 1s–3s 1H and 13C NMR spectra of parent monosaccharides 1–3 and their per-O-sulfated derivatives 1s–3s were recorded in D2O. The signal assignment was performed using 2D COSY and HSQC. J coupling constants were measured directly from 1D 1H NMR spectra. In case of

• overlapping signals J coupling constants were extracted from 2nd order spectra simulations using Bruker TopSpin software (DAISY). The obtained results (see Tables 1–3) showed good coincidence with previously published data for related monosaccharides [15][26][27]. As can be seen from Table 3, J coupling

• preparation. 1H NMR chemical shifts of non-sulfated (1–3a) and per-O-sulfated (1s–3sb) propyl furanosides. 13C NMR chemical shifts of non-sulfated (1–3a) and per-O-sulfated (1s–3sb) propyl furanosides. 1H–1H NMR J coupling constants of non-sulfated (1–3) and per-O-sulfated (1s–3s) propyl furanosides. Low

¹⁵N-Labelling and structure determination of adamantylated azolo-azines in solution

• Sergey L. Deev,
• Alexander S. Paramonov,
• Tatyana S. Shestakova,
• Igor A. Khalymbadzha,
• Oleg N. Chupakhin,
• Julia O. Subbotina,
• Oleg S. Eltsov,
• Pavel A. Slepukhin,
• Vladimir L. Rusinov,
• Alexander S. Arseniev and
• Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

• -ones in acidic conditions occurs through the formation of the adamantyl cation. Keywords: adamantylation; azolo-1,2,4-triazines; J-coupling; 15N-labelled; NMR spectra; 1,2,4-triazolo[1,5-a]pyrimidines; Introduction The incorporation of an adamantyl moiety in bioactive molecules and analogues of

• spectroscopy. For monocyclic derivatives of azoles, the structures of N-alkylated regioisomers can be determined using 2D H-(C)-N multiple bond correlation (HCNMBC) experiments [22][23] using natural isotopic abundance. These experiments rely on the magnetization transfer through 13C-15N J-coupling constants

• ][24][25][26][27][28][29]. The labelling enhances the sensitivity of detection and permits the quantitative measurements of JCN and 1H-15N J-coupling constants (JHN) even in a mixture of tautomeric forms [24][25]. Additionally, a method based on amplitude-modulated spin-echo experiments was found to be

Hydrolysis, polarity, and conformational impact of C-terminal partially fluorinated ethyl esters in peptide models

• Vladimir Kubyshkin and
• Nediljko Budisa

Beilstein J. Org. Chem. 2017, 13, 2442–2457, doi:10.3762/bjoc.13.241

• orientation, respectively [79][80]. This conformational equilibrium manifests in the χ angles, which is reflected by the J-coupling observed between the α-CH and β-CH2 groups in the 1H NMR spectra (Jαβ) [81][82]. A recent analysis of the Jαβ values by Braga et al. was used to quantify the pucker equilibrium

Inclusion complexes of β-cyclodextrin with tricyclic drugs: an X-ray diffraction, NMR and molecular dynamics study

• Franca Castiglione,
• Fabio Ganazzoli,
• Luciana Malpezzi,
• Andrea Mele,
• Walter Panzeri and
• Giuseppina Raffaini

Beilstein J. Org. Chem. 2017, 13, 714–719, doi:10.3762/bjoc.13.70

• experiments in the rotating frame (ROESY) were acquired on 4 mM solutions by using a suitable pulse sequence with two different transmitter offsets for spin-lock and pulse [14] in order to minimize artefacts due to the J-coupling magnetization transfer (HOHAHA). The typical experimental set-up was as follows

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• Information File 1, Figure S19) and the analysis of H–H J coupling and the cross-linking with the data obtained by the COSY and DEPT-ed HSQC spectra (Supporting Information File 1, Figures S21, S22 and Supporting Information File 1, Figure S24, respectively) allowed for a complete assignment of the resonance

Micro-flow synthesis and structural analysis of sterically crowded diimine ligands with five aryl rings

• Shinichiro Fuse,
• Nobutake Tanabe,
• Akio Tannna,
• Yohei Konishi and
• Takashi Takahashi

Beilstein J. Org. Chem. 2013, 9, 2336–2343, doi:10.3762/bjoc.9.268

• ) relative to the signal (0.00 ppm) for internal tetramethylsilane for solutions in CDCl3 (7.26 ppm for 1H, 77.0 ppm for 13C). Multiplicities are reported by using the following abbreviations: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br, broad; and, J, coupling constants in Hertz. IR

Diastereoselective synthesis of nitroso acetals from (S,E)-γ-aminated nitroalkenes via multicomponent [4 + 2]/[3 + 2] cycloadditions promoted by LiCl or LiClO₄

• Leandro Lara de Carvalho,
• Robert Alan Burrow and
• Vera Lúcia Patrocinio Pereira

Beilstein J. Org. Chem. 2013, 9, 838–845, doi:10.3762/bjoc.9.96

• tendency of these frameworks to assume the twist-boat conformation, as shown in X-ray analysis of 11b (Figure 1). According to 1H NMR analysis of all cycloadducts, the protons (H6) showed the highest vicinal J-coupling in the range of 7.3 Hz to 8.0 Hz suggesting a pseudoequatorial arrangement [35]. The