TY  - JOUR
A1  - Benassi, Rois
A1  - Bertarini, C.
A1  - Kleinpeter, Erich
A1  - Taddei, F.
A1  - Thomas, Steffen
T1  - Exocyclic push-pull conjugated compounds : Part 1 ; theoretical study of the effect of ring size on the structure, electronic properties and rotational barriers of cyclic analogoues of 1,1-diamino-2.2-dicyanoethylene
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Benassi, Rois
A1  - Bertarini, C.
A1  - Hilfert, Liane
A1  - Kempter, Gerhard
A1  - Kleinpeter, Erich
A1  - Spindler, Jürgen
A1  - Taddei, F.
A1  - Thomas, Steffen
T1  - Exocyclic push-pull conjugated compounds : Part 3
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Benassi, Rois
A1  - Bertarini, C.
A1  - Kleinpeter, Erich
A1  - Taddei, F.
T1  - Exocyclic push-pull conjugated compounds, Part 2 : the effect of donor and acceptor substituents on the rotational barrier of push-pull ethylenes
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Reiche, K. B.
A1  - Starke, Ines
A1  - Kleinpeter, Erich
A1  - Holdt, Hans-Jürgen
A1  - Pihlaja, Kalevi
A1  - Oksaman, P.
A1  - Ovcharenko, V. V.
T1  - Fragmentation of imine-type meta-bridged bis(benzo crown ether)s under electron impact
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Pihlaja, Kalevi
T1  - Functions containing a thiocarbonyl group and at least one halogen, also at least one chalcogen and no halogen
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Hilfert, Liane
A1  - Koch, Andreas
T1  - GIAO-HF/DFT calculation of C-13 and N-15 chemical shifts for studying tautomerism and intramolecular hydrogen bonding in 2,3-disubstituted quinoxalines
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Baranac-Stojanovic, Marija
A1  - Tatar, Jovanan
A1  - Kleinpeter, Erich
A1  - Markovic, Rade
T1  - High-Yield Synthesis of Substituted and Unsubstituted Pyridinium Salts Containing a 4-Oxothiazolidine Moiety
N2  - A new series of unsubstituted and substituted pyridinium salts bearing a 4-oxothiazolidinyl moiety has been prepared by an efficient rearrangement of 2-(1-bromoalkylidene)thiazolidin-4-ones. The process in based on three steps, namely carbon-bromine cleavage, bromine transfer, and substitution, each induced by pyridine or its derivatives, acting as base and reactant.
Y1  - 2008
ER  - 
TY  - JOUR
A1  - Holdt, Hans-Jürgen
A1  - Drexler, Hans-Joachim
A1  - Starke, Ines
A1  - Grotjahn, Manuela
A1  - Kleinpeter, Erich
T1  - Homologous series of the PdCl2 and PtCl2 complexes of maleonitrile-dithiacrown ethers : synthesis, crystal structures, NMR spectroscopy and mass spectrometry
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Reiche, K. B.
A1  - Starke, Ines
A1  - Kleinpeter, Erich
A1  - Holdt, Hans-Jürgen
T1  - Host-guest complexation of imine-type meta-bridged bis(benzo crown ether)s with alkali cations in the gas phase under FAB conditions
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Rolla, Nadja
A1  - Koch, Andreas
A1  - Taddei, Fernando
T1  - Hyperconjugation and the increasing bulk of OCOCX3 substituents in trans-1,4-disubstituted cyclohexanes destabilize the diequatorial conformer
N2  - The trans diesters of 1,4-cyclohexanediol with a number of acetic acid analogues, CX3COOH, of varying steric hindrance and polarity (CX3 = Me, Et, iso-Pr, tert-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, CBr3) were synthesized, and the axial, axial/equatorial, equatorial conformational equilibria were studied by low-temperature H-1 NMR spectroscopy in CD2Cl2. The structures and relative energies of the axial, axial and equatorial, equatorial conformers were calculated at both the MP2/6-311G* and the MP2/6-311+G* levels of theory, and it was only by including diffuse functions that a good correlation of Delta G degrees(calcd) vs Delta G(exptl) could be obtained. Both the structures and the energy differences of the axial, axial and equatorial, equatorial conformers are discussed with respect to the established models of conformational analysis, viz., steric 1,3-diaxial and hyperconjugative interactions. Interestingly, the hyperconjugative interactions sigma(C-C)/sigma(C-H)->sigma*(C-O), together with a steric effect which also destabilizes the equatorial, equatorial conformers on increasing bulk of the substituents, proved to dominate the position of the conformational equilibria. In addition, the preference of the axial, axial conformers with respect to their equatorial, equatorial analogues was greater than expected from the conformational energies of the corresponding substituents in the monosubstituted cyclohexyl esters. The reason for this very interesting and unexpected result is also discussed
Y1  - 2006
UR  - http://pubs.acs.org/journal/joceah
U6  - https://doi.org/10.1021/Jo0600858
SN  - 4393-4399
ER  - 
TY  - JOUR
A1  - Nitschke, Felix
A1  - Wang, Peixiang
A1  - Schmieder, Peter
A1  - Girard, Jean-Marie
A1  - Awrey, Donald E.
A1  - Wang, Tony
A1  - Israelian, Johan
A1  - Zhao, XiaoChu
A1  - Turnbull, Julie
A1  - Heydenreich, Matthias
A1  - Kleinpeter, Erich
A1  - Steup, Martin
A1  - Minassian, Berge A.
T1  - Hyperphosphorylation of glucosyl C6 carbons and altered structure of glycogen in the neurodegenerative epilepsy lafora disease
JF  - Cell metabolism
N2  - Laforin or malin deficiency causes Lafora disease, characterized by altered glycogen metabolism and teenage-onset neurodegeneration with intractable and invariably fatal epilepsy. Plant starches possess small amounts of metabolically essential monophosphate esters. Glycogen contains similar phosphate amounts, which are thought to originate from a glycogen synthase error side reaction and therefore lack any specific function. Glycogen is also believed to lack monophosphates at glucosyl carbon C6, an essential phosphorylation site in plant starch metabolism. We now show that glycogen phosphorylation is not due to a glycogen synthase side reaction, that C6 is a major glycogen phosphorylation site, and that C6 monophosphates predominate near centers of glycogen molecules and positively correlate with glycogen chain lengths. Laforin or malin deficiency causes C6 hyperphosphorylation, which results in malformed long-chained glycogen that accumulates in many tissues, causing neurodegeneration in brain. Our work advances the understanding of Lafora disease pathogenesis and suggests that glycogen phosphorylation has important metabolic function.
Y1  - 2013
U6  - https://doi.org/10.1016/j.cmet.2013.04.006
SN  - 1550-4131
SN  - 1932-7420
VL  - 17
IS  - 5
SP  - 756
EP  - 767
PB  - Cell Press
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Stamboliyska, Bistra A.
T1  - Hyperpolarizability of donor-acceptor azines subject to push-pull character and steric hindrance
N2  - The push-pull character of two series of donor-acceptor azines has been quantified by C-13, N-15 chemical shift differences of the partial C(1)=N(1) and N(2)=C(2) double bonds in the central linking C(1)=N(1)-N(2)=C(2) unit and by the quotient of the occupations of the bonding pi and anti-bonding pi* orbitals of these bonds. Excellent correlation of the latter push-pull parameter with the corresponding bond lengths d(C=N) strongly recommend both the occupation quotients pi*/pi and the corresponding bond lengths as reasonable sensors for quantifying the push, pull character along the C=N-N=C linking unit, for the donor-acceptor quality of the two series of azines and for the molecular hyperpolarizability beta(0) of these compounds. Within this context, reasonable conclusions concerning the interplay of steric hindrance in the chromophore, push-pull character and hyperpolarizability of the azines and their application as NLO materials will be drawn.
Y1  - 2009
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2009.09.026
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Identification of benzenoid and quinonoid structures by through-space NMR shieldings (TSNMRS)
Y1  - 2010
SN  - 1089-5639
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Identification of mesomeric substructures by through-space NMR shieldings (TSNMRS). Trimethine cyanine/merocyanine-like or aromatic pi-electron delocalization?
JF  - Tetrahedron
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of amino-substituted heteraromatic six-membered ring systems such as pyrylium/thiopyrylium analogues have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values were employed to quantify and visualize the existing aromaticity of the studied compounds. Due to strong conjugation of six-membered ring pi-electrons and lone pairs of the exo-cyclic amino substituents (restricted rotation about partial C,N double bonds) the interplay of still aromatic and already dominating trimethine cyanine/merocyanine-like substructures can be estimated. (C) 2017 Elsevier Ltd. All rights reserved.
KW  - Through-space NMR shieldings (TSNMRS)
KW  - GIAO
KW  - NICS
KW  - Benzenoid structures
KW  - Cyanine/merocyanine-like structures
KW  - Aromaticity
Y1  - 2017
U6  - https://doi.org/10.1016/j.tet.2017.05.062
SN  - 0040-4020
VL  - 73
SP  - 4265
EP  - 4274
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Lämmermann, Anica
A1  - Szatmári, István
A1  - Fulop, Ferenc
A1  - Kleinpeter, Erich
T1  - Inter- or intramolecular N···H-O or N-H···O Hydrogen bonding in 1,3-Amino-alpha/beta-naphthols : an experimental NMR and computational study
N2  - The existence of intermolecular or intramolecular N···H;O or N;H···O hydrogen bonding in three series (series 1, substituted 1-aminoalkyl-2-naphthols: R = H, Me, Et, Pr, i-Pr; series 2, substituted 1-;- aminobenzyl-2-naphthols: H, p-OMe, p-F, p-Cl, p-Br, p-NO2, p-Me; series 3, substituted 2-;-aminobenzyl-1-naphthols: R = H, p-Me, p-F, p-Br, p-OMe, m-NO2, m-Br) are studied by NMR spectroscopy and computed at the DFT level of theory [B3LYP/6-311+G(d,p)]. The correct nature of the H-bond was assigned unequivocally both experimentally and computationally by potential energy scans rotating the involved dihedral angles. We investigated the effects of substituents on the strength of the H-bond by evaluating the corresponding hyperconjugative stabilization energy nlonepair ; ;*X;H and Hammett substituent constant plots. By this means, steric and electronic substituent effects could be easily quantified and separated.
Y1  - 2009
UR  - http://pubs.acs.org/journal/jpcafh
U6  - https://doi.org/10.1021/Jp902731n
SN  - 1089-5639
ER  - 
TY  - JOUR
A1  - Thomas, Steffen
A1  - Kleinpeter, Erich
T1  - Internet und World Wide Web : Nutzen für den NMR Spektroskopiker
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
A1  - Schulz, Stefanie
A1  - Wacker, Philipp
T1  - Interplay of para- and diatropic ring currents [(anti)aromaticity] of macrocyclic rings subject to conformational influences, further annelation and hydrogenation of aromatic ring moieties
JF  - Tetrahedron
N2  - The spatial magnetic properties (Through Space NMR Shieldings-TSNMRS) of a variety of porphyrins, hemiporphyrazines and tetraoxo[8]circulenes have been computed, visualized as Iso-chemical Shielding Surfaces (ICSS) of various size and direction, and were examined subject to the interplay of present (para)-diatropic ring currents [(anti)aromaticity] and influences on the latter property originating from the macrocyclic ring conformation, further annelation and partial to complete hydrogenation of aromatic ring moieties. Caution seems to be indicated when concluding from a single NICS parameter to present (para)diatropic ring currents [(anti)aromaticity]. (C) 2014 Elsevier Ltd. All rights reserved.
KW  - Porphyrins
KW  - Hemiporphyrazines
KW  - Tetraoxo[8]circulenes
KW  - (Anti)aromaticity
KW  - Anisotropy effect
KW  - Theoretical calculations
Y1  - 2014
U6  - https://doi.org/10.1016/j.tet.2014.10.018
SN  - 0040-4020
VL  - 70
IS  - 48
SP  - 9230
EP  - 9239
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Seidl, Peter Rudolf
A1  - Carneiro, J. W. D.
A1  - Tostes, J. G. R.
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Interpretation of conformational effects on 2-endo-norborneol by natural chemical shielding analysis
N2  - This paper represents an extension of our work on the H-1 and C-13 NMR chemical shifts of norbornane and 2-endo- norborneol. NCS-NBO analysis was employed to probe contributions of bond orbitals and orbitals of lone pairs to nuclear shielding in conformers of the alcohol generated by rotation of the C-O bond. Variations in H-1 and C-13 chemical shifts with the dihedral angle are discussed in terms of Lewis and non-Lewis partitioning and their respective importance is evaluated. In addition to hyperconjugation of the lone pair in a p orbital of oxygen that was previously reported, a sizable participation of the lone pair which is in an sp orbital is also observed and their combined effect dominates the carbon chemical shifts of the C-1-C-2-OH and C-3-C-2-OH fragments. Both lone pairs on oxygen also contribute to localized, though-space effects on nuclei in the vicinity, these effects answering for the largest deviations in hydrogen chemical shifts on rotation around the C-O bond. On the other hand, for conformers in which nonbonded repulsions lead to distortions in the molecular framework, variations in chemical shifts may be attributed to angular effects
Y1  - 2005
SN  - 1089-5639
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Intramolecular carbene stabilization via 3c,2e bonding on basis of the magnetic criterion
JF  - Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of bent cyclobutylcarbene 8, 1,2-diboretane-3-ylidene 9, and some carbene analogues of boron 14-18 as most intriguing examples of carbenes, which can be stabilized as homoaromatic systems with 3c,2e bonding, have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually, ring current effect/anisotropy effects as measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the degree of present 3c,2e-homoaromaticity. Results are confirmed by geometry (bond angles and bond lengths) and spectroscopic data, the delta(B-11)/ppm data and the C-13 chemical shifts of the carbene electron-deficient centre.
KW  - Cyclobutylcarbene
KW  - 1,2-diboretane-3-ylidene
KW  - 3c,2e-bonding
KW  - Through-space NMR shieldings (TSNMRS)
KW  - NICS
Y1  - 2021
U6  - https://doi.org/10.1016/j.tet.2021.132357
SN  - 0040-4020
SN  - 1464-5416
VL  - 95
PB  - Elsevier Science
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Baranac-Stojanovic, Marija
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Is the conventional interpretation of the anisotropic effects of C=C double bonds and aromatic rings in NMR spectra in terms of the p-electron shielding/deshielding contributions correct?
JF  - Chemistry - a European journal
N2  - Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10 angstrom away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C?C double bond or the aromatic ring should not be explained in terms of the conventionally accepted p-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.
KW  - ab initio calculations
KW  - anisotropic effects
KW  - NMR spectroscopy
KW  - nucleus-independent chemical shift
KW  - pi interactions
Y1  - 2012
U6  - https://doi.org/10.1002/chem.201101882
SN  - 0947-6539
VL  - 18
IS  - 1
SP  - 370
EP  - 376
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Branac-Stojanovi, Marija
A1  - Koch, Andreas
T1  - Is the Conventional Interpretation of the Anisotropic Effects of CC Double Bonds and Aromatic Rings in NMR Spectra in Terms of the -Electron Shielding/Deshielding Contributions Correct?
N2  - Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10;Å away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the C=C double bond or the aromatic ring should not be explained in terms of the conventionally accepted ;-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.
Y1  - 2012
SN  - 1521-3765
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Is the term "Carbene" justified for remote N-heterocyclic carbenes (r-NHCs) and abnormal N-heterocyclic carbenes (aNHCs/MICs)?
JF  - Tetrahedron
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of typical N-heterocyclic carbenes NHCs, r-NHCs, a-NHCs and MICs have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. Prior to that both structures and 13C chemical shifts were calculated and in case of isolated carbenes the computed δ(13C)/ppm values compared (as a quality criterion for obtained structures) with the experimental ones. The TSNMRS values of the studied carbenes, which are in mesomeric equilibrium with zwitterionic (ylide/betaine/mesoionic) resonance contributors, are employed to qualify and quantify the present electronic structure and if the term carbene is still justified to denote the compounds studied. The results, thus obtained from spatial magnetic properties (TSNMRS), are compared with the geometry of the compounds, the corresponding WIBERG's bond index values, and the 13C chemical shifts especially of the carbene electron-deficient centre.
KW  - Carbene or zwitterions
KW  - Ylide
KW  - Mesomeric equilibrium of carbene/zwitterion
KW  - Through-space NMR shieldings (TSNMRS)
KW  - NICS
Y1  - 2019
U6  - https://doi.org/10.1016/j.tet.2019.02.005
SN  - 0040-4020
VL  - 75
IS  - 11
SP  - 1548
EP  - 1554
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Fettke, Anja
A1  - Kramer, Markus
A1  - Kleinpeter, Erich
T1  - Lectin-bound conformations and non-covalent interactions of glycomimetic analogs of thiochitobiose
N2  - The bound conformations of five S-glycoside analogs of N,N'-diacetylchitobiose as well as their non- covalent interactions with two lectins, Phytolacca americana lectin (PAL) and wheat germ agglutinin (WGA), are reported. The conformations of the ligands were examined by trNOESY experiments and compared with the free, solution-state conformations and molecular modeling data obtained by force field calculations. In the case of S-aryl, S-glycosides with exclusively S-glycosidic linkages, similar free and lectin-bound conformations and non-covalent interactions were found, whereas they differed for mixed glycosides and for a thiazoline derivative. In addition, STD (saturation transfer difference) NMR magnetization transfer efficiencies at three different temperatures were determined and assessed with respect to the structural differences of these pseudosaccharides. The binding epitopes of each substrate with PAL and WGA were also determined.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2010.04.012
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Starke, Ines
A1  - Schuster, Ildikkó
A1  - Fulop, Ferenc
A1  - Kleinpeter, Erich
T1  - Mass spectra of tetrahydroisoquinoline-fused 1,3,2-O,N,P- and 1,2,3-O,S,N-heterocycles: influence of ring size and fusion, of present heteroatoms, substituent effects and of the stereochemistry on fra
N2  - The electron ionization (EI) mass spectra of a variety of stereoisomeric tricyclic 1,3,2-oxazaphosphino[4,3- a]isoquinolines (1-4), 1,2,3-oxathiazino[4,3-a]isoquinoline-4-oxides (5-7) and the -4,4-dioxides (8-10) of oxazaphospholo- and oxathiazolo[4,3-a]- (11, 12, 15 and 16) and -[3,4-b]isoquinolines (13, 14 and 17) were recorded. Ring size and fusion, the different heteroatoms (P and S) and substituents on the ring systems strongly influence the mass spectra. In addition, mass spectra of the stereoisomers of compounds 1, 2 and 13, 14 revealed stereochemically relevant differences which are not observed for the other pairs of isomers. Copyright © 2008 John Wiley & Sons, Ltd.
Y1  - 2008
ER  - 
TY  - JOUR
A1  - Sardarian, Ali Reza
A1  - Inaloo, Iman Dindarloo
A1  - Modarresi-Alam, Ali Reza
A1  - Kleinpeter, Erich
A1  - Schilde, Uwe
T1  - Metal-Free Regioselective Monocyanation of Hydroxy-, Alkoxy-, and Benzyloxyarenes by Potassium Thiocyanate and Silica Sulfuric Acid as a Cyanating Agent
JF  - The journal of organic chemistry
N2  - A novel and efficient metal- and solvent-free regioselective para-C-H cyanation of hydroxy-, alkoxy-, and benzyloxyarene derivatives has been introduced, using nontoxic potassium thiocyanate as a cyanating reagent in the presence of silica sulfuric acid (SSA). The desired products are obtained in good to high yields without any toxic byproducts.
Y1  - 2019
U6  - https://doi.org/10.1021/acs.joc.8b02191
SN  - 0022-3263
VL  - 84
IS  - 4
SP  - 1748
EP  - 1756
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Grotjahn, Manuela
A1  - Drexler, Hans-Joachim
A1  - Jäger, Norbert
A1  - Kleinpeter, Erich
A1  - Holdt, Hans-Jürgen
T1  - Molecular dynamic and conformational study of an unsaturated 12-crown-S202 ether and its AgI complexes
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Grotjahn, Manuela
A1  - Jäger, Norbert
A1  - Drexler, Hans-Joachim
A1  - Holdt, Hans-Jürgen
A1  - Kleinpeter, Erich
T1  - Molecular modeling study of the PtCl2 complexes of unsaturated S2On+1- coronands: dynamic simulations and investigation of the ring interconversion
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Belyakov, Alexander V.
A1  - Sigolaev, Yurii F.
A1  - Khramov, Alexander N.
A1  - Kleinpeter, Erich
T1  - Molecular Structure and Conformational Analysis of 1-Phenyl-1-X-1-Silacyclohexanes (X = F, Cl) by Electron Diffraction, Low-Temperature NMR, and Quantum Chemical Calculations
JF  - The journal of organic chemistry
N2  - The molecular structure and conformational preferences of 1-phenyl-1-X-1-silacyclohexanes C5H10Si(Ph,X) (X = F (3), Cl (4)) were studied by gas-phase electron diffraction, low-temperature NMR spectroscopy, and high-level quantum chemical calculations. In the gas phase only three (3) and two (4) stable conformers differing in the axial or equatorial location of the phenyl group and the angle of rotation about the Si-C-ph bond (axi and axo denote the Ph group lying in or out of the X-Si-C-ph plane) contribute to the equilibrium. In 3 the ratio Ph-eq:Ph-axo:Ph-axi is 40(12):55(24):5 and 64:20:16 by experiment and theory, respectively. In 4 the ratio Ph-eq:Ph-axo is 79(15):21(15) and 71:29 by experiment and theory (M06-2X calculations), respectively. The gas-phase electron diffraction parameters are in good agreement with those obtained from theory at the M06-2X/aug-ccPVTZ and MP2/aug-cc-pVTZ levels. Unlike the case for M06-2X, MP2 calculations indicate that 3-Ph-eq conformer lies 0.5 kcal/mol higher than the 3-Ph-axo, conformer. As follows from QTAIM analysis, the phenyl group is more stable when it is located in the axial position but produces destabilization of the silacyclohexane ring: By low temperature NMR spectroscopy the six-membered ring interconversion could be frozen, at 103 K and the present conformational equilibria of 3 and 4 could be determined. The ratio of the conformers is 3-Ph-eq:3-Ph-ax = (75-77):(23-25) and 4-Ph-eq:4-Ph-ax = 82:18.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.joc.6b02538
SN  - 0022-3263
VL  - 82
IS  - 1
SP  - 461
EP  - 470
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Kirpichenko, Svetlana V.
A1  - Kleinpeter, Erich
A1  - Shlykov, Sergey A.
A1  - Osadchiy, Dmitriy Yu.
T1  - Molecular structure and conformational analysis of 3-methyl-3-phenyl-3-silatetrahydropyran. Gas-phase electron diffraction, low temperature NMR and quantum chemical calculations
JF  - Tetrahedron
N2  - The molecular structure and conformational behavior of 3-methyl-3-phenyl-3-silatetrahydropyran 1 was studied by gas-phase electron diffraction (GED-MS), low temperature C-13 NMR spectroscopy (LT NMR) and theoretical calculations. The 1-Ph-eq and 1-Ph-ax conformers were located on the potential energy surface. Rotation about the Si-C-ph bond revealed the phenyl ring orthogonal to the averaged plane of the silatetrahydropyran ring for 1-Ph-eq and a twisted orientation for 1-Ph-ax. Theoretical calculations and GED analysis indicate the predominance of 1-Ph-ax in the gas phase with the ratio of conformers (GED) 1-Ph-eq:1-Ph-ax=38:62 (Delta G degrees(307)=-0.29 kcal/mol). In solution, LT NMR spectroscopy gives almost the opposite ratio Ph-eq:1-Ph-ax=68:32 (Delta G degrees(103)=0.16 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of compound 1 in the gas phase and in solution. (C) 2015 Elsevier Ltd. All rights reserved.
KW  - 3-Silatetrahydropyrans
KW  - Conformational analysis
KW  - Low temperature NMR spectroscopy
KW  - Gas-phase electron diffraction
KW  - Quantum chemical calculations
Y1  - 2015
U6  - https://doi.org/10.1016/j.tet.2015.03.117
SN  - 0040-4020
VL  - 71
IS  - 23
SP  - 3810
EP  - 3818
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Haufe, G.
A1  - Rolle, U.
A1  - Kleinpeter, Erich
A1  - Kivikoski, J.
A1  - Rissanen, K.
T1  - N-Heterocyclization in electrophilic haloamination reactions of 1,5-cyclooctadiene : formation of the granatanine and homotropane skeletons
Y1  - 1993
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Ushakov, Igor A.
A1  - Tolstikova, Ljudmila L.
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - N-Trifyl substituted 1,4-diheterocyclohexanesùstereodynamics and the Perlin effect
N2  - The stereodynamic behaviour of 1-(trifluoromethylsulfonyl)piperidine 1, 4-(trifluoromethylsulfonyl)morpholine 2, 1,4-bis(trifluoromethylsulfonyl)piperazine 3 and 4-(trifluoromethylsulfonyl)thiomorpholine 1,1-dioxide 4 was studied by low-temperature 1H, 13C and 19F NMR spectroscopies. In acetone solution, compounds 1, 2 and 4 were found to exist as mixtures of two conformers in the ratio of 4:1, 4:1 and 8:1, respectively, differing by orientation of the CF3 group with respect to the ring. Compound 3 exists as a mixture of three conformers in the ratio of 3:28:69 also differing by the orientation of the two CF3 groups. Unlike the previously studied N-trifyl substituted 1,3,5-triheterocyclohexanes, the preferred conformers of compound 1 and of 1,4-diheterocyclohexanes 2-4 are those with the CF3 group directed outward from the ring, which is caused by intramolecular interactions of the oxygen atoms of the CF3SO2N groups with the equatorial hydrogens in the ;-position. B3LYP/6-311+G(d,p) calculations of the energy, geometry and NMR parameters corroborate the experimental data. The calculated Perlin effects for all conformers of compounds 1-4 as well as those measured for the major conformers of compounds 3 and 4 were analyzed by the use of the NBO analysis.
Y1  - 2008
ER  - 
TY  - JOUR
A1  - Neuvonen, Kari
A1  - Neuvonen, Helmi
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Nature of the steric Omega(S), E-R and E-S ' substituent constants -  comparison with the aid of NBO and STERIC analysis
JF  - Computational and theoretical chemistry
N2  - The nature of the major steric substituent constant scales for alkyl substituents, i.e. Omega(S), E-R and E-S' scales, was studied with the aid of the NBO and the natural steric (STERIC) analyses. Cyclohexyl esters R-3-CCOOC6H11 (R = alkyl or H) were used as the model compounds. Special emphasis was laid on the potential contribution of the polar component in these steric substituent parameters. In the light of our model the Omega(S) scale seems to be dominantly a steric substituent constant scale as is seen on the strengths of the good correlation between the Omega(S) constants of the CR3 group and the total steric exchange energy values E-TSEE for the model compounds. However, the Omega(S) values also seem to include a minor electronic component due to the varying electrostatic effect via the C alpha atom. On the other hand, E-R and E-S' parameters largely hinge on the size dependent polar effect of the CR3 alkyl group. By way of our model this repulsive interaction can be quantified by descriptor Delta q(OCO), the natural charge difference q(C)(C=O) - Sigma qO for the O-C(=O) functional group. Delta q(OCO) depends on the E-TSEE values, on qC alpha and on the polarization coefficients of the oxygen hybrid in the NBO of the pi(C=O) bond. The size sensitivity of the kinetic E-S' constants can be connected to variation of the Burgi-Dunitz angle in the transition state for the standard reaction used. A comparison is made for the q(C)(C=O) or Delta q(OCO) values computed on the one hand with the NBO formalism and on the other hand with the Hirshfeld formalism. A practical novel substituent constant q(C)(C=O) for the size of the alkyl groups is introduced.
KW  - NBO and STERIC analyses
KW  - Taft equation
KW  - Steric substituent constant
KW  - Steric effect
KW  - Polar effect
Y1  - 2013
U6  - https://doi.org/10.1016/j.comptc.2013.03.025
SN  - 2210-271X
VL  - 1015
IS  - 4
SP  - 34
EP  - 43
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Neuvonen, Kari
A1  - Neuvonen, Helmi
A1  - Koch, Andreas
T1  - NBO analysis of polar and steric effect using the axial-equatorial equilibrium of cyclohexyl acetates as a probe
Y1  - 2011
SN  - 2210-271X
ER  - 
TY  - JOUR
A1  - Neuvonen, Kari
A1  - Neuvonen, Helmi
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - NBO analysis of polar and steric effect using the axial-equatorial equilibrium of cyclohexyl acetates as a probe
JF  - Computational and theoretical chemistry
N2  - The proportion of the axial conformer increases in the ax reversible arrow eq equilibrium of cyclohexyl acetates (RCOOC(6)H(11), R reversible arrow Me, Et, iPr, tBu, CH(2)Cl, CHCl(2), CO(3). CH(2)Br, CHBr(2), CBr(3)) with the increasing size of the acyloxy substitution. The nature of this unexpected steric substituent effect, which is opposite to general stereochemical concepts, was studied by means of ab kiln MO method, accompanied by NBO and isodesmic calculations. NBO parameters seem to be good descriptors for quantitative prediction of the experimental Delta G degrees value of the title conformational equilibrium. The origin and propagation of the substituent effect of the polar substitutions (CH(2)Cl, CHCl(2), CCl(3), CH(2)Br, CHBr(2), CBr(3)) differ, however, from those of the pure alkyl (Me, Et, iPr, tBu) substitutions. The Delta G degrees value of the polar derivatives depends on the qC8 charges, on the occupation of the sigma(center dot)(C1-07) orbital and on the hyperconjugative pi(center dot)(c=O) -> sigma(center dot)(C10-X) and sigma(center dot)(C10-X) -> pi(center dot)(c=O) interactions. The substituent sensitivity of these NBC parameters for the two conformers differ to the effect that the ax reversible arrow eq equilibrium is shifted to the left side with increasing electron withdrawing character of the acyloxy group. The Delta G degrees values of the alkyl derivatives are interpreted in terms of the calculated dipole moments. The destabilization in the non-polar medium (the experimental Delta G degrees values used were measured in CD(2)Cl(2)) due to the enhanced dipolar character is more prominent in the case of the equatorial alkyl conformers. As the consequence, the ax reversible arrow eq equilibrium is shifted to the left despite the increasing size of the R group when going from Me to tBu substitution.
KW  - Substituent effects
KW  - Ab initio MO computations
KW  - Conformational equilibria
KW  - Cyclohexyl esters
KW  - NBO analysis
Y1  - 2011
U6  - https://doi.org/10.1016/j.comptc.2010.12.033
SN  - 2210-271X
VL  - 964
IS  - 1-3
SP  - 234
EP  - 242
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Hilfert, Liane
A1  - Koch, Andreas
T1  - NMR spectroscopic and ab-initio MO study of sterically hindered 2,3-disubstituted quinoxalines
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Grotjahn, Manuela
A1  - Lehmann, S.
A1  - Aurich, Ines
A1  - Holdt, Hans-Joachim
A1  - Kleinpeter, Erich
T1  - NMR spectroscopic and molecular modelling studies of the solution structure and complexational behaviour of some bis(benzocrown ether)s
N2  - Structural information about the bis(benzo crown ether)s I-VI and their complexes with alkali metal cations was deduced from the 13C NMR chemical shifts, the salt-induced 1H and 13C chemical shifts and the vicinal 1H,1H coupling constants. Especially the isomerism with respect to the amide O=C - NH bonds and imine fragments were assigned by various useful NMR parameters ( C=O, 1JN,H, 1JC,H) and proved to be E,E-anti,anti. Furthermore, stereochemical information about preferred conformations about flexible bonds was obtained from 2D ROESY NMR experiments. The complex formation (2:1 complexes and sandwich-like 1:1 complexes, respectively) were determined also by 23Na NMR spectroscopy. The conformational study of the crown ethers was accompanied and corroborated by molecular dynamics and quantum chemical calculations.
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Holzberger, Anja
A1  - Holdt, H. N.
A1  - Kleinpeter, Erich
T1  - NMR spectroscopic and molecular modelling study of the solution structure and the complexational behavior of maleonitrile tetrathia crown ethers with silver(I)
N2  - The flexibility and complex formation of two maleonitrile tetrathia crown ethers were studied in solution using H-1 and C-13 NMR spectroscopy and molecular modelling. Both the stoichiometry and the stability of the complexes that these crown ethers form with Ag(I) were determined by NMR titration measurements. Spin-lattice relaxation time measurements provided information concerning the donor atoms involved in complex formation and also the intramolecular mobility of the free and complexed ligands. Molecular modelling was also used to gain further insight into the conformational space of the free ligands and their silver(I) complexes. Copyright (C) 2004 John Wiley Sons, Ltd
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Heydenreich, Matthias
A1  - Kalder, L.
A1  - Koch, Andreas
A1  - Henning, Dietrich
A1  - Kempter, Gerhard
T1  - NMR spectroscopic and theoretical structural analysis of 5,5-disubstituted hydantoins in solution
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Heydenreich, Matthias
A1  - Kalder, L.
A1  - Koch, Andreas
A1  - Henning, Dietrich
A1  - Kempter, Gerhard
A1  - Benassi, Rois
A1  - Taddei, F.
T1  - NMR spectroscopic and theoretical structural analysis of 5,5-disubstituted hydantoins in solution
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Benassi, Rois
A1  - Bregulla, Antje
A1  - Friedrich, Alwin
A1  - Henning, Dietrich
A1  - Heydenreich, Matthias
A1  - Mickler, Wulfhard
A1  - Kleinpeter, Erich
A1  - Kempter, Gerhard
A1  - Schilde, Uwe
A1  - Taddei, F.
T1  - NMR spectroscopic and theoretical structural study of 5-exo-methylene-substituted hydantoins
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Germer, Antje
A1  - Klod, Sabrina
A1  - Peter, Martin G.
A1  - Kleinpeter, Erich
T1  - NMR spectroscopic and theoretical study of the complexation of the inhibitor allosamidin in the binding pocket of the plant chitinase hevamine
N2  - Based on NMR spectroscopic information about the allosamidin-hevamine complex, ab initio MO calcns. of the ring current effect of the arom. moieties of Trp255, Tyr183 and Tyr6 of hevamine were carried out to investigate the role of these amino acid residues in binding interactions with allosamidin in soln. In addn., the intermol. steric compression effect on the 13C chem. shifts of the allosamizoline carbon atoms and the hydrogen bonding to Glu127 was identified. It can be inferred that the binding forces are strongest in the allosamizoline moiety of allosamidin.
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Krtitschka, Angela
A1  - Krüger, Tobias
A1  - Linker, Torsten
T1  - NMR spectroscopic conformational analysis of 4-methylene-cyclohexyl pivalateThe effect of sp(2) hybridization
JF  - Magnetic resonance in chemistry
N2  - The conformational equilibrium of the axial/equatorial conformers of 4-methylene-cyclohexyl pivalate is studied by dynamic NMR spectroscopy in a methylene chloride/freon mixture. At 153K, the ring interconversion gets slow on the nuclear magnetic resonance timescale, the conformational equilibrium (-G degrees) can be examined, and the barrier to ring interconversion (G(#)) can be determined. The structural influence of sp(2) hybridization on both G degrees and G(#) of the cyclohexyl moiety can be quantified.
KW  - 4-methylene-cyclohexyl pivalate
KW  - conformational analysis
KW  - dynamic NMR spectroscopy
KW  - exo-methylene conformational effect at cyclohexane
KW  - quantum chemical calculations
Y1  - 2017
U6  - https://doi.org/10.1002/mrc.4630
SN  - 0749-1581
SN  - 1097-458X
VL  - 55
SP  - 1073
EP  - 1078
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Starke, Ines
A1  - Ströhl, D.
A1  - Holdt, Hans-Jürgen
T1  - NMR spectroscopic study of the solution structure and complexational behaviour of bis-benzocrown ethers
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Starke, Ines
A1  - Ströhl, D.
A1  - Holdt, Hans-Jürgen
T1  - NMR spectroscopic study of the solution structure and complexational behaviour of bis-benzocrown ethers
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Benassi, Rois
A1  - Bregulla, Antje
A1  - Henning, Dietrich
A1  - Heydenreich, Matthias
A1  - Kempter, Gerhard
A1  - Kleinpeter, Erich
A1  - Taddei, F.
T1  - NMR-spectroscopic and theoretical structural analysis of 5-benzyl subtituted hydantoins in solutions
Y1  - 1999
ER  - 
TY  - BOOK
A1  - Kleinpeter, Erich
T1  - NMR-Spektoskopie : Struktur, Dynamik und Chemie des Moleküls
Y1  - 1992
PB  - Barth
CY  - Leipzig
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
T1  - NMR-Spektroskopie
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Csuetoertoeki, Renata
A1  - Szatmari, Istvan
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Starke, Ines
A1  - Fueloep, Ferenc
A1  - Kleinpeter, Erich
T1  - Novel piperidine-fused benzoxazino- and
 quinazolinonaphthoxazines-synthesis and conformational study
JF  - TETRAHEDRON
N2  - The reactions of 1-(amino(2-hydroxyphenyl)methyl)-2-naphthol (3) and 1-(amino(2-aminophenyl) methyl)-2-naphthol (6) with glutardialdehyde resulted in the formation of piperidine-fused benzox-azinonaphthoxazine 4 and quinazolinonaphthoxazine 7, respectively, both in diastereopure form. The full conformational search protocols of 4 and 7 were successfully carried out by NMR spectroscopy and accompanying molecular modelling; the global minimum-energy conformers of all diastereomers were computed, and the assignments of the most stable stereoisomers, G(tct)(1) for 4 and G(tct)(1) for 7, were corroborated by spatial NOE information relating to the H-7a-H-10a-H-15b and H,H coupling patterns of the protons in the flexible part of the piperidine moiety. Additionally, mass spectrometric fragmentation was investigated in collision-induced dissociation experiments. The elemental compositions of the ions were determined by accurate mass measurements. (C) 2012 Elsevier Ltd. All rights reserved.
KW  - Quinazolines
KW  - Naphthoxazines
KW  - DFT structural study
KW  - Conformational analysis
KW  - NMR spectroscopy
Y1  - 2012
U6  - https://doi.org/10.1016/j.tet.2012.05.048
SN  - 0040-4020
VL  - 68
IS  - 31
SP  - 6284
EP  - 6288
PB  - PERGAMON-ELSEVIER SCIENCE LTD
CY  - OXFORD
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Csütörtöki, Renáta
A1  - Szatmári, István
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Starke, Ines
A1  - Fulop, Ferenc
T1  - Novel piperidine-fused benzoxazino- and quinazolinonaphthoxazines-synthesis and conformational study
N2  - The reactions of 1-(amino(2-hydroxyphenyl)methyl)-2-naphthol (3) and 1-(amino(2-aminophenyl)methyl)-2-naphthol (6) with glutardialdehyde resulted in the formation of piperidine-fused benzoxazinonaphthoxazine 4 and quinazolinonaphthoxazine 7, respectively, both in diastereopure form. The full conformational search protocols of 4 and 7 were successfully carried out by NMR spectroscopy and accompanying molecular modelling; the global minimum-energy conformers of all diastereomers were computed, and the assignments of the most stable stereoisomers, Gtct1 for 4 and Gtct1 for 7, were corroborated by spatial NOE information relating to the H7a-H10a-H15b and H,H coupling patterns of the protons in the flexible part of the piperidine moiety. Additionally, mass spectrometric fragmentation was investigated in collision-induced dissociation experiments. The elemental compositions of the ions were determined by accurate mass measurements.
Y1  - 2012
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Starke, Ines
A1  - Koch, Andreas
A1  - Uhlemann, Erhard
A1  - Kleinpeter, Erich
T1  - Nuclear-magnetic-resonance studies and molecular modelling of the solution structure of some dibenzo crown- ethers and their complexes
Y1  - 1995
ER  -