Molecular cleft or tweezer compounds derived from trioxabicyclo[3.3.1]nonadiene diisocyanate and diacid dichloride

• Gert Kollenz,
• Ralf Smounig,
• Ferdinand Belaj,
• David Kvaskoff and
• Curt Wentrup

Beilstein J. Org. Chem. 2015, 11, 1–8, doi:10.3762/bjoc.11.1

• with arbitrary radii; the other H atoms as well as the disordered atoms with site occupation factors less than 0.5 were omitted for the sake of clarity. The intramolecular hydrogen bond is indicated by a dashed line (H(N32)–O40 = 1.970 Å). Stereoscopic ORTEP plot of molecule B of 4 with atomic

• numbering scheme. The ellipsoids are drawn at the 50% probability level. The H atoms bonded to N are drawn with arbitrary radii; the other H atoms as well as the disordered atoms with site occupation factors less than 0.5 were omitted for reasons of clarity. The intramolecular hydrogen bond is indicated by

Synthesis and immunological evaluation of protein conjugates of Neisseria meningitidis X capsular polysaccharide fragments

• Laura Morelli,
• Damiano Cancogni,
• Marta Tontini,
• Alberto Nilo,
• Sara Filippini,
• Paolo Costantino,
• Maria Rosaria Romano,
• Francesco Berti,
• Roberto Adamo and
• Luigi Lay

Beilstein J. Org. Chem. 2014, 10, 2367–2376, doi:10.3762/bjoc.10.247

• , when the hemiacetal 6 was treated with salicylchlorophosphite in pyridine at room temperature the α-H-phosphonate 7 was obtained as a single anomer in only 2 h in 62% yield. We reasoned that the occurrence of an intramolecular hydrogen bond involving the acetamido group could be the main responsible

De novo macrolide–glycolipid macrolactone hybrids: Synthesis, structure and antibiotic activity of carbohydrate-fused macrocycles

• Richard T. Desmond,
• Anniefer N. Magpusao,
• Chris Lorenc,
• Jeremy B. Alverson,
• Nigel Priestley and
• Mark W. Peczuh

Beilstein J. Org. Chem. 2014, 10, 2215–2221, doi:10.3762/bjoc.10.229

• (defined as the torsional angle about the C5’–C6’ bond) is in the gt conformation for each structure [27]. An intramolecular hydrogen bond between the C4’ hydroxy group and the C3’ oxygen is also apparent in 5 whereas in 6 the same hydroxy group is hydrogen-bonded to a bound water molecule. Observations

Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect

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

Beilstein J. Org. Chem. 2014, 10, 877–882, doi:10.3762/bjoc.10.84

• 10.3762/bjoc.10.84 Abstract The gauche effect in fluorinated alkylammonium salts is well known and attributed either to an intramolecular hydrogen bond or to an electrostatic attraction between the positively charged nitrogen and the vicinal electronegative fluorine atom. This work reports the effect of

• participation of intramolecular hydrogen bond and hyperconjugation. These findings can be useful to predict the structure and stereochemistry of multifluorinated organic compounds with, e.g., pharmaceutical and/or agrochemical interest. Experimental 2,2-Difluoroethylamine hydrochloride (2) was purchased from

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• 15.9(3)°, 11.1(3)°, 0.6(3)° for the first three ester groups (C6–C7–C8–O5, C6–C7–C12–O7, C3–C2–C10–O3) and 152.28(17)° for the last one (O1–C1–C2–C3) (Supporting Information File 1, Table S5). N5–H5A forms an intramolecular hydrogen bond with O3 and an intermolecular hydrogen bond with O4. N6–H6A forms

• an intramolecular hydrogen bond with O5, while both also form an intermolecular hydrogen bond with O5 from the next molecule as shown in Table S2. These two hydrogen bonds are in a rhomboid arrangement with angles H6A–O5–H6A 86.10(5)° and O5–H6A–O5 93.90(5)°. Selected interatomic distances, bond and

• into a doublet (3J = 11.0 Hz) due to the coupling with the alkene-H (δ 8.05 ppm). The ester moiety involved in the intramolecular hydrogen bond exhibits a marked downfield shift for C=O (δ 168.5 ppm) in comparison to the other ester carbonyl C-atom (δ 164.7 ppm), which is typical for such a situation

Conformation of dehydropentapeptides containing four achiral amino acid residues – controlling the role of L-valine

• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Maciej Makowski,
• Rafał Latajka and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 660–666, doi:10.3762/bjoc.10.58

• that it is involved in an intramolecular hydrogen bond. In the case of peptide 3, the temperature factor of the amide proton of ΔAla(2) is slightly higher than the threshold indicating the presence of hydrogen bonding. Such a value could suggest that the amide proton of ΔAla(2) is at least partially

New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

• Helge Klare,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2014, 10, 224–236, doi:10.3762/bjoc.10.18

• were obtained from catalysts 6 and 7a. Both catalysts form dimers with short intermolecular hydrogen bonds between P1O1–H3 and P2O2–H2 (1.843/1.810 Å and 2.148/2.103 Å respectively, Figure 3 and Figure 4). In each case the second acidic NH proton H1 forms an intramolecular hydrogen bond to quinuclidin

• nitrogen N1, which is significantly shorter in 7a (2.194/2.110 Å respectively). The intramolecular hydrogen bond is probably also the cause for the occurrence of conformational isomers when inverting the configuration at C9. While catalyst (S)-4 solely exists as one conformer on the NMR timescale, its

• , which was confirmed by DOSY and temperature-dependent NMR (Supporting Information File 1). The cause is probably the hindered rotation by the intramolecular hydrogen bond N1–H1. Synthesis of chiral PV-cyclodiphosphazane amides In order to synthesize chiral cyclodiphosphazanes 14a/14b, PCl5 was reacted

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• the key role of intramolecular hydrogen bond (H-bond) interactions for both reactivity and stereoselectivity [65]. Theoretical calculations and experimental evidences ruled out the SN1 reaction mechanism via allylic carbocation. Experiments with stereodefined hydroxy allylic alcohols revealed that the

Synthesis and characterization of novel bioactive 1,2,4-oxadiazole natural product analogs bearing the N-phenylmaleimide and N-phenylsuccinimide moieties

• Catalin V. Maftei,
• Elena Fodor,
• Peter G. Jones,
• M. Heiko Franz,
• Gerhard Kelter,
• Heiner Fiebig and
• Ion Neda

Beilstein J. Org. Chem. 2013, 9, 2202–2215, doi:10.3762/bjoc.9.259

• compound 6 was also confirmed by X-ray structure analysis (Figure 10 and Figure 11). In compound 6 the interplanar angle is 11°; the intramolecular hydrogen bond is almost symmetrical (O4–H04 1.03(3), H04···O2 1.47(3)) Å. The molecules are linked to form layers perpendicular to the hexagonal c axis by one

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

• František Josefík,
• Markéta Svobodová,
• Valerio Bertolasi and
• Petr Šimůnek

Beilstein J. Org. Chem. 2013, 9, 1463–1471, doi:10.3762/bjoc.9.166

•  1 (Table S1). A selection of bond distances and angles and the intramolecular hydrogen bond parameters are also reported in Supporting Information File 1 (Table S2 and Table S3). Conclusion We have developed an improved simple methodology for the construction of bicyclic pyridazinium

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