Conformational analysis and intramolecular interactions in monosubstituted phenylboranes and phenylboronic acids

• Josué M. Silla,
• Rodrigo A. Cormanich,
• Roberto Rittner and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2013, 9, 1127–1134, doi:10.3762/bjoc.9.125

• show positive ρ(r) values and negative H(r) values (Table 2), indicating a strong, partially covalent intramolecular hydrogen bond. The remaining criteria established by Koch and Popelier [23] are also satisfied, namely q(H), M1(H), V(H) and E(H) (Table 3), which were obtained by integration of the

• high hyperconjugative stabilization compared to 1c and lower steric repulsion compared to 1b; also, it is greatly favored by an F∙∙∙HO intramolecular hydrogen bond. This information can be theoretically checked by comparing the geometries of 1 and 2 (where F∙∙∙HO intramolecular hydrogen bonding is not

• possible): while 2b is more stable than 2c, because it prevents the interaction between the oxygen lone pairs, 1b is more stable than 1c, even exhibiting such a repulsive interaction, because 1b allows a F∙∙∙HO intramolecular hydrogen bond. The lack of intermolecular hydrogen bonding and the presence of

Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• the best pharmacokinetic profile in normal mice with high brain uptake and a washout rate, that was 8 times faster than that of [11C]56c. Interestingly, it was noted that the 4-OH analogue 56u could form an intramolecular hydrogen bond (i.e. an extra pseudo ring), which could act to increase the

Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

• Matthias Leven,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18

• structure of 5 (Figure 1). A characteristic detail in the X-ray crystallographic structure of 5 is the intramolecular hydrogen bond between H10 and O3 (distance: 2.283 Å) in Figure 1, which restricts the conformation of the 2-sulfobenzoic moiety. It was found that the solubility of each precatalyst shown in

The diketopiperazine-fused tetrahydro-β-carboline scaffold as a model peptidomimetic with an unusual α-turn secondary structure

• Francesco Airaghi,
• Andrea Fiorati,
• Giordano Lesma,
• Manuele Musolino,
• Alessandro Sacchetti and
• Alessandra Silvani

Beilstein J. Org. Chem. 2013, 9, 147–154, doi:10.3762/bjoc.9.17

• molecular modeling and these experimental results, for 1a we can presume the presence in solution of conformers bearing a 13-membered intramolecular hydrogen bond involving the NHMe proton and the Cbz carbonyl group, as visualized in the perspective view of the low energy conformer of 1a. Conclusion In

A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors

• El Sayed H. El Ashry,
• El Sayed H. El Tamany,
• Mohy El Din Abdel Fattah,
• Mohamed R. E. Aly,
• Ahmed T. A. Boraei and
• Axel Duerkop

Beilstein J. Org. Chem. 2013, 9, 135–146, doi:10.3762/bjoc.9.16

• )–C(16)–N(2) = 2.2(4)°. The molecular conformation is stabilized by an intramolecular hydrogen bond O(4)–H(4)···O(3) and a water molecule links two molecules in the crystal lattice through an intermolecular hydrogen bond O(6)–H(6P)···S(1). Conclusion In conclusion, 2-N-(glycosyl)thiosemicarbazides of

Inclusion of the insecticide fenitrothion in dimethylated-β-cyclodextrin: unusual guest disorder in the solid state and efficient retardation of the hydrolysis rate of the complexed guest in alkaline solution

• Dyanne L. Cruickshank,
• Natalia M. Rougier,
• Raquel V. Vico,
• Susan A. Bourne,
• Elba I. Buján,
• Mino R. Caira and
• Rita H. de Rossi

Beilstein J. Org. Chem. 2013, 9, 106–117, doi:10.3762/bjoc.9.14

• -polygon; D, the glycosidic O4···O4′ distance; Φ the O4···O4′···O4′′ angle; d, the O4···O4′···O4′′···O4′′′ torsion angle; α, the deviation of each O4 atom from the O4 mean plane; D3, the O2···O3′ intramolecular hydrogen bond distance; tilt angle τ1, the angle between the six atoms of the glucopyranose ring

Influence of intramolecular hydrogen bonds on the binding potential of methylated β-cyclodextrin derivatives

• Gerhard Wenz

Beilstein J. Org. Chem. 2012, 8, 1890–1895, doi:10.3762/bjoc.8.218

• entropy. In contrast, primary hydroxy groups in β-CD are too far apart from each other to allow intramolecular hydrogen-bond formation. Hydrogen bonds between primary hydroxy groups were only found for α-CD, leading to a conical host conformation, which is unfavorable for the accommodation of a guest [45

Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols

• Fátima M. P. de Rezende,
• Marilua A. Moreira,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2012, 8, 1227–1232, doi:10.3762/bjoc.8.137

• intramolecular hydrogen bond in the syn-exo isomer. It was found through NBO and AIM analyses that such an interaction contributes to structural stabilization and that the 1hJF,H(O) coupling constant in the syn-exo isomer is modulated by the nF→σ*OH interaction, i.e., the quantum nature of the F∙∙∙HO hydrogen

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• counterparts in toluene solution, e.g., 31 min for cis-11 versus 650 ms for cis-14 (Figure 15). This can be understood bearing in mind that azocompound 11 should undergo dimerization prior to its isomerisation in toluene. Nevertheless, the formation of an intramolecular hydrogen bond [62] in the ortho

Laterally substituted symmetric and nonsymmetric salicylideneimine-based bent-core mesogens

• Sonja Findeisen-Tandel,
• Wolfgang Weissflog,
• Ute Baumeister,
• Gerhard Pelzl,
• H. N. Shreenivasa Murthy and
• Channabasaveshwar V. Yelamaggad

Beilstein J. Org. Chem. 2012, 8, 129–154, doi:10.3762/bjoc.8.15

• ) or the central phenyl ring (CH3) on the liquid-crystalline behaviour and on the physical properties is studied. Corresponding benzylideneaniline-based compounds were additionally prepared in order to study the influence of the intramolecular hydrogen bond. The occurring mesophases were investigated

• the synthesis of bent-core salicylideneaniline compounds bearing a lateral methyl group at the central phenyl ring, in search of further materials that may also show the unusual multistage switching as mentioned above. To assess the effect of the intramolecular hydrogen bond on the mesophase behaviour

• stabilization effect is already well-known from calamitic Schiff bases and is caused by the intramolecular hydrogen bond, which could also reduce the flexibility of this molecular leg. Halogen substituents in position X have only a modest effect on the mesophase stability. A slight decrease in the clearing

Computational evidence for intramolecular hydrogen bonding and nonbonding X···O interactions in 2'-haloflavonols

• Tânia A. O. Fonseca,
• Matheus P. Freitas,
• Rodrigo A. Cormanich,
• Teodorico C. Ramalho,
• Cláudio F. Tormena and
• Roberto Rittner

Beilstein J. Org. Chem. 2012, 8, 112–117, doi:10.3762/bjoc.8.12

• found to be dictated mainly by a C=O···H–O intramolecular hydrogen bond, but an unusual C–F···H–O hydrogen-bond and intramolecular C–X···O nonbonding interactions are also present in such compounds. Keywords: conformational analysis; 2'-haloflavonols; intramolecular hydrogen bond; nonbonding

Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit

• Jens Eckelmann,
• Vittorio Saggiomo,
• Svenja Fischmann and
• Ulrich Lüning

Beilstein J. Org. Chem. 2012, 8, 11–17, doi:10.3762/bjoc.8.2

• increased with respect to the non-preorganized isophthalamides. However, an intramolecular hydrogen bond can be easily broken in polar solvents, hence destroying the preorganization and thus decreasing the binding affinities for the anions. Herein we describe the facile synthesis and the binding properties

Anthracene appended pyridinium amide–urea conjugate in selective fluorometric sensing of L-N-acetylvaline salt

• Kumaresh Ghosh,
• Tanmay Sarkar and
• Asoke P. Chattopadhyay

Beilstein J. Org. Chem. 2010, 6, 1211–1218, doi:10.3762/bjoc.6.139

• pyridinium para proton (Hp) showed a small downfield shift (Δδ = 0.02–0.48). This small change in chemical shift of the para proton is due to either a change in bond length of the intramolecular hydrogen bond between the amide carbonyl oxygen and para hydrogen of pyridinium motif, or involvement in the

The C–F bond as a conformational tool in organic and biological chemistry

• Luke Hunter

Beilstein J. Org. Chem. 2010, 6, No. 38, doi:10.3762/bjoc.6.38

• an intramolecular hydrogen bond helping to stabilise the gauche conformers of 8 and 9, but the gauche preference is also maintained in systems such as 10 (Figure 1b) which cannot accommodate a hydrogen bond [10], confirming that the charge–dipole interaction is more important than any weak H-bonding

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Synthesis and binding studies of two new macrocyclic receptors for the stereoselective recognition of dipeptides

• Ana Maria Castilla,
• M. Morgan Conn and
• Pablo Ballester

Beilstein J. Org. Chem. 2010, 6, No. 5, doi:10.3762/bjoc.6.5

• macrocycle, also allows for the possibility of binding short amino acid sequences not necessarily located on the edges of larger peptides. Other considerations, apart from preventing intramolecular hydrogen bond formation, related to the use of bis(alanyl)benzophenone rigid linkers include: a) to avoid

Reactions of glycidyl derivatives with ambident nucleophiles; part 2: amino acid derivatives

• Gerald Dyker,
• Andreas Thöne and
• Gerald Henkel

Beilstein J. Org. Chem. 2007, 3, No. 28, doi:10.1186/1860-5397-3-28

• from a weak intramolecular hydrogen bond. According to ab initio calculations for cis-9a, (B3LYP, 6-31G*, zero point energy included) this structure is indeed 1.9 kcal/mol more stable than its exo-oriented conformer and 2.2 kcal/mol more stable than its trans-stereoisomer. Conclusion In summary, we

8-epi-Salvinorin B: crystal structure and affinity at the κ opioid receptor

• Thomas A. Munro,
• Katharine K. Duncan,
• Richard J. Staples,
• Wei Xu,
• Lee-Yuan Liu-Chen,
• Cécile Béguin,
• William A. Carlezon Jr. and
• Bruce M. Cohen

Beilstein J. Org. Chem. 2007, 3, No. 1, doi:10.1186/1860-5397-3-1

• other possible C8/9/12 stereochemistries (trans/anti, trans/syn and cis/syn) – the furan is equatorial in all cases.[17] The rest of the structure is very similar to the crystal structure of 1a.[1] The hydroxyl group participates in an intramolecular hydrogen bond with the ketone (O2-H2···O1, 2.12 Å

Crystal engineering of analogous and homologous organic compounds: hydrogen bonding patterns in trimethoprim hydrogen phthalate and trimethoprim hydrogen adipate

• Packianathan Thomas Muthiah,
• Savarimuthu Francis,
• Urszula Rychlewska and
• Beata Warżajtis

Beilstein J. Org. Chem. 2006, 2, No. 8, doi:10.1186/1860-5397-2-8

• pyrimethamine hydrogen maleate [21] and pyrimethamine hydrogen succinate [21] are isomorphous since the hydrogen succinate is the saturated analogue of hydrogen maleate. The hydrogen succinate ion adopts a folded conformation with an intramolecular hydrogen bond (mimicking the hydrogen maleate ion) leading to