BACKGROUND The proton at position 5 of imidazo[1,2-a]pyridines substituted with an angular electron withdrawing group (EWG) at position 3, shows an unusual downfield chemical shift, which is usually explained in terms of a peri effect. However usage of this term is sometimes confusing. In this investigation, it is proposed that the aforementioned shift is in fact a combination of several factor...

The title compound, C(9)H(9)BrN(2)O(2), crystallizes with two independent but essentially identical mol-ecules in the asymmetric unit. Each mol-ecule adopts a trans configuration with respect to the C=N bond. In one of the mol-ecules, the dihedral angle between the benzene ring and the hydrazinecarboxylic acid plane is 24.9 (2)°, and that in the other mol-ecule is 16.1 (2)°. The mol-ecules are ...

The title compound, erioflorin, C19H24O6 [systematic name: (1aR,3S,4Z,5aR,8aR,9R,10aR)-1a,2,3,5a,7,8,8a,9,10,10a-deca-hydro-3-hy-droxy-4,10a-dimethyl-8-methyl-idene-7-oxooxireno[5,6]cyclo-deca-[1,2-b]furan-9-yl methacrylate], is a tricyclic germacrane sesquiterpene lactone, which was isolated from Podanthus mitiqui (L.). The compound crystallizes in the space group P212121, and its mol-ecular s...

In the title salt, C(12)H(11)N(2)O(2) (+)·C(7)H(5)O(6)S(-), the dihedral angle between the benzene and pyridine rings in the 4-(4-nitro-benz-yl)pyridinium cation is 82.7 (2)°. Within the anion there is an intramolecular hydroxy-O-H⋯O(carboxylic acid) bond. In the crystal, the cation forms a single N(+)-H⋯O(sulfonate) hydrogen bond with the anion. These cation-anion pairs inter-act through duple...

T 9 S synthesized, where X = Gly (l), L-Ala (2), D-Ala (3), Aib (4) and L&U (5). ‘H NMR studies at 270 MHz in CDCI, and (CD@0 provide evidence of a Pro-X /?-turn conformation, stabilized by a transannular 4-l hydrogen bond involving the Cys(4) NH, in all the peptides. In addition peptides 2,4 and 5 also possess a second intramolecular hydrogen bond involving the -NHMe group. The spectroscopic d...

Four diastereoisomers of 2-fluorobicyclo[2.2.1]heptan-7-ols were computationally investigated by using quantum-chemical calculations, and their relative energies were analyzed on the basis of stereoelectronic interactions, particularly the presence or otherwise of the F∙∙∙HO intramolecular hydrogen bond in the syn-exo isomer. It was found through NBO and AIM analyses that such an interaction co...

In the structure of the title salt, C(12)H(10)N(3)O(4) (+)·C(7)H(3)N(2)O(7) (-), the cations and the anions are linked by a single N(+)-H⋯O(carbox-yl) hydrogen bond, the discrete cation-anion unit having no inter-molecular associations other than weak cation-anion aromatic ring π-π inter-actions [ring centroid separation = 3.7320 (14) Å] and a number of weak inter-unit aromatic C-H⋯O contacts. ...

Carboxyphosphate, a suspected intermediate in ATP-dependent carboxylases, has not been isolated nor observed directly by experiment. Consequently, little is known concerning its structure, stability, and ionization state. Recently, carboxyphosphate as either a monoanion or dianion has been shown computationally to adopt a novel pseudochair conformation featuring an intramolecular charge-assiste...

The computational insights illustrate the intramolecular hydrogen bonding/stability versus aromaticity analyses of a variety several sets multi-substituted OH/SH benzenes using quantifying approaches (NICS, HOMA, PDI, and AIBIC for aromaticity) (Relative Energy, HOMO-LUMO gap, QTAIM, HBSBIC stability/hydrogen bond strength) in framework density function theory (DFT) approach ab initio calculati...

Different strategies are employed in designing strong and selective anion receptors but stereoelectronic effects have been largely ignored. In this work, the stereo configuration of a non-interacting ether is found to have a large impact of more than two orders of magnitude on the binding of a rigid diol with tetrabutylammonium chloride in acetonitrile-d3. A favorable carbon-oxygen dipole and a...