@article{FettkePeikowPeteretal.2009,
  author    = {Fettke, Anja and Peikow, Dirk and Peter, Martin G. and Kleinpeter, Erich},
  title     = {Synthesis and conformational analysis of glycomimetic analogs of thiochitobiose},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2009.03.067},
  year      = {2009},
  abstract  = {The synthesis of six analogs of N,N;-diacetylchitobiose is reported, including a novel transglycosylation reaction for the preparation of S-aryl thioglycosides. The conformations of the compounds were studied by a combination of NMR spectroscopy and molecular modeling, using force field calculations. In the case of the S-aryl thioglycosides with exclusively S-glycosidic linkages, dihedral angles of the disaccharidic S-glycosidic bonds, ;; and ;; and of the S-arylglycoside bonds, ; and ;, were found to be similar, whereas they were different in mixed glycosides and in a thiazoline derivative. An adequate correlation between the calculated H,H-distances of the local minima and the measured NOE contacts was achieved by applying population-weighted averages over participating conformers based on weighted relative energies.},
  language  = {en}
}
@article{ShainyanFettkeKleinpeter2008,
  author    = {Shainyan, Bagrat A. and Fettke, Anja and Kleinpeter, Erich},
  title     = {Push-pull vs captodative aromaticity},
  issn      = {1089-5639},
  doi       = {10.1021/jp804999m},
  year      = {2008},
  abstract  = {Vinylogs of fulvalenes with cyclopropenyl and cyclopentadienyl moieties attached either to different carbon atoms (c-C3H2-CH-CH=C5H4-c, 7) or to the same carbon atom [X=C(c-C3H2)(c-C5H4), 10] [X = CH2; C(CN)2; C(NH2)2; C(OCH2)2; O; c-C3H2; c-C5H4; SiH2; CCl2] of the double bond inserted between the two rings are examined theoretically at the B3LYP/ 6;311G(d,p) level. Both types of compounds are shown to possess aromaticity, which was called "push;pull" and "captodative" aromaticity, respectively. For the captodative mesoionic structures X=C(c-C3H2)(c-C5H4), the presence of both the two aromatic moieties and the C=C double bond is the necessary and sufficient condition for their existence as energetic minima on the potential energy surface. Aromatic stabilization energy (ASE) was assessed by the use of homodesmotic reactions and heats of hydrogenation. Spatial magnetic criteria (through space NMR shieldings, TSNMRS) of the two types of vinylogous fulvalenes 7 and 10 have been calculated by the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept of Paul von Ragu{\´e}; Schleyer, and visualized as iso-chemical-shielding surfaces (ICSS) of various sizes and directions. TSNMRS values can be successfully employed to visualize and quantify the partial push;pull and captodative aromaticity of both the three- and five-membered ring moieties. In addition, the push;pull effect in compounds 7 and 10 could be quantified by the occupation quotient ;*C=C/;C=C of the double bond inserted between the two rings.},
  language  = {en}
}
@article{KihampaNkunyaJosephetal.2009,
  author    = {Kihampa, Charles and Nkunya, Mayunga H. H. and Joseph, Cosam C. and Magesa, Stephen M. and Hassanali, Ahmed and Heydenreich, Matthias and Kleinpeter, Erich},
  title     = {Anti-mosquito and antimicrobial nor-halimanoids, isocoumarins and an anilinoid from Tessmannia densiflora},
  issn      = {0031-9422},
  doi       = {10.1016/j.phytochem.2009.07.024},
  year      = {2009},
  abstract  = {The nor-halimane diterpenoid tessmannic acid and its methyl, 2-methylisopropyl and 1-methylbutyl esters, the unusual isocoumarins 8-hydroxy-6-methoxy-3-pentylisocoumarin and 7-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin, and 5- pentyl-3-methoxy-N-butylaniline were isolated from the stem and root bark extracts of Tessmannia densiflora Harms (Caesalpiniaceae) that showed mosquito larvicidal activity. The structures were determined on interpretation of spectroscopic data. Tessmannic acid and its methyl ester exhibited antibacterial and antifungal activity. The compounds also caused high larvae and adult Anopheles gambiae mosquitoe mortality effects, and stronger mosquito repellency than that shown by the standard repellent DEET, hence indicating Tessmannia species to be potential sources of bioactive natural products.},
  language  = {en}
}
@article{KleinpeterKoch2009,
  author    = {Kleinpeter, Erich and Koch, Andreas},
  title     = {pi-delocalization in oligoalkynes induced by push-pull substituents and 1,3-conjugation : a combined 13C NMR and computational study ; dedicated to Prof. Alan R. Katritzky},
  issn      = {1089-5639},
  doi       = {10.1021/Jp905873f},
  year      = {2009},
  abstract  = {13C chemical shifts of the push;pull oligoalkynes Don-(C;C)n-Acc (n = 1;4; Don = morpholino; Acc = COMe, COOMe) were computed at the DFT (B3LYP/6-311+G(d,p) level of theory compared with the experimental ; values and the agreement employed as a measure of quality for the underlying structures. For the global minima structures, the occupation quotients of antibonding ;* and bonding ; orbitals (;*C;C/ ;C;C) and the bond lengths (dC;C) of the various C;C triple bonds were also computed and correlated to each other. The linear dependence obtained for the two parameters dC;C and ;*C;C/ ;C;C quantifies changes in ;-delocalization induced by the push;pull effect of the substituents and 1,3-conjugation (1,3,5- and 1,3,5,7-, respectively) of the C;C bonds in the oligoalkynes studied. A critical comparison of the push;pull effect, attenuated with increasing n, and the conjugative stabilization of the oligoalkynes, increasing with n, as concluded from dC;C and ;*C;C/;C;C of the oligoalkynes and the reference compounds Me-(C;C)n-Me, Don-(C;C)n-Me, and Me-(C;C)n-Acc), respectively (Don = morpholino; Acc = COMe, COOMe), is affiliated.},
  language  = {en}
}
@article{WackerKleinpeter2007,
  author    = {Wacker, Philipp and Kleinpeter, Erich},
  title     = {Stoichiometry, complex stability, molecular size and conformational variations of metal ion crown ether complexes subject to diffusion coefficients in nonaqueous solutions},
  doi       = {10.1007/s10847-007-9332-1},
  year      = {2007},
  abstract  = {Both the stoichiometry and complex stability constants of crown ether complexes with metal ions have been determined by examining gradual changes in their diffusional behavior in nonaqueous solution. Diffusion coefficients, D, were evaluated by pulsed field gradient (PFG) NMR titration experiments whilst complex stability constants were determined by nonlinear curve-fitting procedures, D versus csol., which also allow the treatment of multiple complexation equilibria (1:1 to 1:2 stoichiometries). Differences in the diffusion coefficients of the various free crown ethers with respect to their metal ion complexes indicate great sensitivity to both conformational changes and changes in molecular size upon complexation.},
  language  = {en}
}
@article{SzatmariTothKochetal.2006,
  author    = {Szatmari, Istvan and Toth, Diana and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc},
  title     = {Study of the substituent-influenced anomeric effect in the ring-chain tautomerism of 1-alkyl-3-aryl-naphth[1,2- e][1,3]oxazines},
  doi       = {10.1002/ejoc.200600563},
  year      = {2006},
  abstract  = {The stabilities of the trans (B) and cis (C) tautomeric ring forms that are experimentally observed in the ring- chain tautomeric interconversion of 1-alkyl-3-aryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines has been investigated. Stability differences are explained by the analysis of the natural bond orbital results for the lone pairs of electrons that are on the heteroatoms in the oxazine ring system and by regression analysis of the calculated 13C NMR chemical shift values.},
  language  = {en}
}
@article{SarodnickLinkerHeydenreichetal.2009,
  author    = {Sarodnick, Gerhard and Linker, Torsten and Heydenreich, Matthias and Koch, Andreas and Starke, Ines and F{\"u}rstenberg, Sylvia and Kleinpeter, Erich},
  title     = {Quinoxalines XV : convenient synthesis and structural study of pyrazolo[1,5-alpha]quinoxalines},
  issn      = {0022-3263},
  doi       = {10.1021/Jo802398g},
  year      = {2009},
  abstract  = {A series of aryloxymethylquinoxaline oximes, hitherto unknown and synthesized from the corresponding aldehydes, afforded in only one step pyrazolo[1,5-;]quinoxalines in the presence of acetic anhydride at high temperatures. A formal [3,5]-sigmatropic rearrangement was proposed as the mechanistic rationale for this unprecedented transformation. Saponification with potassium hydroxide furnished the free phenol derivatives which were studied by NMR spectroscopy and accompanying theoretical DFT calculations, establishing intramolecular hydrogen bonding and the spatial magnetic properties. Additionally, mass spectrometric fragmentation was investigated by B/E-linked scans and collision-induced dissociation experiments. The fragmentation pattern devoted a new gas phase rearrangement process, which proved to be unique and characteristic for pyrazolo[1,5-;]quinoxalines.},
  language  = {en}
}
@article{KleinpeterFrank2009,
  author    = {Kleinpeter, Erich and Frank, Andrea},
  title     = {Distinction of Push,pull effect and steric hindrance in disubstituted alkynes},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2009.03.075},
  year      = {2009},
  abstract  = {The push,pull effect in two series of disubstituted alkynes was studied at the DFT level [B3LYP/6-311G(d)] by application of the 13C chemical shift differences (GIAO) between the alkyne carbon atoms (Delta delta (C C)), the charge difference between these carbons (Delta q(C C)), the occupation quotient (NBO) of anti-bonding pi*, and bonding pi orbitals (pi*(C C)/pi(C C)) and the bond length (d(C C)) of the C C triple bond. The linear dependence of d(C C) versus pi*(C C)/pi(C C) quantifies changes in the push,pull effect while deviations from the latter correlation indicate and ascertain quantitatively to what extent steric hindrance restricts the strain-less conjugation of the C C triple bond pi- orbitals in the disubstituted alkynes.},
  language  = {en}
}
@article{BoehmTomaszcikovaImrichetal.2009,
  author    = {B{\"o}hm, Stanislav and Tomaszcikov{\´a}, Jana and Imrich, J{\´a}n and Danihel, Ivan and Kristian, Pavol and Koch, Andreas and Kleinpeter, Erich and Klika, Karel D.},
  title     = {Computational study to assign structure, tautomerism, E/Z and s-cis/s-trans isomerism, pi-delocalization, partial aromaticity, and the ring size of 1,3-thiazolidin-4-ones and 1,3-thiazin-4-ones formed from thiosemicarbazides},
  issn      = {0166-1280},
  year      = {2009},
  abstract  = {A set of structures encompassing 1-(9-acridinyl)thiosemicarbazide and its 2-methyl derivative together with their various tautomeric structures; the 5-membered ring 1,3-thiazolidin-4-one products resulting from the reaction of 1- (9-acridinyl)thiosemicarbazide and its 2-methyl derivative with dimethyl acetylenedicarboxylate (DMAD) together with the alternative 6-membered ring isomeric reaction products as well as other potential isomeric structures; and the 6- membered ring 1,3-thiazin-4-one product resulting from the reaction of 2-methyl-1-(9-acridinyl)thiosemicarbazide with methyl propiolate (MP) together with the alternative 5-membered ring isomeric reaction product were all extensively studied by molecular modeling calculations using DFT at the B3LYP/6-31G(d,p) level of theory. The ring-chain tautomerism of the thiosemicarbazides, the regio- and stereoselectivity of the reactions, the adopted conformations and E/Z configurations of the products, the prototropic tautomerism of all the compounds, and the reasons for the predominance of the s-cis conformation of the Z configuration of the 1,3-thiazolidin-4-one product in particular were all extensively analyzed. Comparison of the modeled structures were also made to the 1,3-thiazolidin-4-one and 1,3-thiazin-4-one structures of the methyl derivative as well as 1-(9-acridinyl)thiosemicarbazide available from X-ray crystallographic analysis. Tactics utilizing spectroscopic methods {IR frequencies (;) and NMR chemical shifts (;), scalar coupling constants (J), and NOEs (;)} in conjunction with molecular modeling calculations of the spectral parameters {frequency calculations (;) and NMR ; using the GIAO method and J by calculation of the Fermi contact term} were evaluated in terms of proving 5- or 6-membered ring formation.},
  language  = {en}
}
@article{ModarresiAlamAlsadatAmiraziziBagherietal.2009,
  author    = {Modarresi-Alam, Ali Reza and Alsadat Amirazizi, Homeyra and Bagheri, Hajar and Bijanzadeh, Hamid-Reza and Kleinpeter, Erich},
  title     = {Dynamic 1H NMR spectroscopic study of the ring inversion in N-sulfonyl morpholines-studies on N-S interactions},
  issn      = {0022-3263},
  year      = {2009},
  abstract  = {The effect of the exocyclic conjugation, via d;p orbital interaction and/or negative hyperconjugation (anomeric effect) of the N;S bond, on the inversion of the morpholine ring in some N-arylsulfonyl morpholines is studied by variable-temperature 1H NMR spectroscopy in different solvents. The observed free energy barriers are 9.2;10.3 kcal mol;1; the lower values were obtained with increasing conjugation (substituents of higher electron withdrawing power) along the series. The barrier to ring inversion of 1e was solvent independent. X-ray data of compounds 1b,d reveal the chair conformation of the six-membered ring, the flattened pyramidal orientation of the ring nitrogen atom, and the sulfonyl group in equatorial position with the plane containing the Caryl;S;N bond perpendicular to the plane of the benzene ring. In addition, the sulfonamide group prefers a conformation with the S;C bond antiperiplanar with respect to the nitrogen atom lone pair and the ;CH2;N;CH2; moieties in staggered conformation with the S;O bonds of the SO2 group.},
  language  = {en}
}
@article{KleinpeterFrank2009,
  author    = {Kleinpeter, Erich and Frank, Andrea},
  title     = {Quantification of the push-pull effect in substituted alkynes : evaluation of +/- I/+/- M substituent effects in terms of C C bond length variation},
  issn      = {1089-5639},
  doi       = {10.1021/Jp9024359},
  year      = {2009},
  abstract  = {C-13 chemical shifts of alkynes, published to date, were computed at the DFT (B3LYP/6-311G*) level of theory and compared with the experimental delta values, and the agreement was employed as a measure of quality for the underlying structures. For the corresponding global minima structures, thus obtained, the occupation quotients of antibonding pi* and bonding pi orbitals (pi*(C C)/pi(C C)) and the bond lengths (d(C C)) of the central C C triple bond were computed and correlated to each other. The linear dependence obtained for the two push-pull parameters d(C C) and pi*(C C)/pi(C C) quantifies changes in the push-pull effect of substituents while deviations from the best line of fit indicate and ascertain quantitatively to what extend the inductive (+/-l) substituent effect changes with respect to the bond length of the C C triple bond.},
  language  = {en}
}
@article{KleinpeterSzatmariLazaretal.2009,
  author    = {Kleinpeter, Erich and Szatm{\´a}ri, Istv{\´a}n and L{\´a}z{\´a}r, L{\´a}szl{\´o} and Koch, Andreas and Heydenreich, Matthias and Fulop, Ferenc},
  title     = {Visualization and quantification of anisotropic effects on the 1H NMR spectra of 1,3-oxazino[4,3- alpha]isoquinolines - indirect estimates of steric compression},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2009.07.038},
  year      = {2009},
  abstract  = {The anisotropic effects of the phenyl, alpha- and beta-naphthyl moieties in four series of 1,3-oxazino[4,3- a]isoquinolines on the H-1 chemical shifts of the isoquinoline protons were calculated by employing the Nucleus Independent Chemical Shift (NICS) concept and Visualized as anisotropic cones by a through-space NMR shielding grid. The signs and extents of these spatial effects on the H-1 chemical shifts of the isoquinoline protons were compared with the experimental H-1 NMR spectra. The differences between the experimental delta (H-1)/ppm values and the calculated anisotropic effects of the aromatic moieties are discussed in terms of the steric compression that occurs in the Compounds studied.},
  language  = {en}
}
@article{FechnerKramerKleinpeteretal.2009,
  author    = {Fechner, Mabya and Kramer, Markus and Kleinpeter, Erich and Koetz, Joachim},
  title     = {Polyampholyte-modified ionic microemulsions},
  issn      = {0303-402X},
  doi       = {10.1007/s00396-009-2074-4},
  year      = {2009},
  abstract  = {This paper is focused on the influence of added polyampholyte, namely poly(N,N;-diallyl-N,N;- dimethyl-alt-maleamic carboxylate) on the inverse micellar phase range of the pseudo-ternary system consisting of toluene-pentanol (1:1)/SDS/water in dependence on the pH value and the temperature. Investigations on phase behavior have revealed that a greater extension in direction to the water-rich corner can be found at pH 4 compared to pH 9. In order to understand changes in the microstructure, polymer-surfactant interactions in dependence on pH have been examined by means of diffusion-ordered spectroscopy, differential scanning calorimetry, as well as conductivity measurements. The results have proven that the present microemulsion consists of water-in-oil droplets, with the polyampholyte located more in the inner core of the water droplets at pH 9 rather than at the interphase of the surfactant film at pH 4.},
  language  = {en}
}
@article{KleinpeterHartmannSchrothetal.1992,
  author    = {Kleinpeter, Erich and Hartmann, J{\"u}rgen and Schroth, W. and Hofer, O. and Kalchhauser, H. and Wurz, G.},
  title     = {Synthesis and conformational behaviour of Ditosyldiaza[2.2]orthometacyclophanes},
  year      = {1992},
  language  = {en}
}
@article{KleinpeterStohssSchroth1992,
  author    = {Kleinpeter, Erich and Stohß, S. and Schroth, W.},
  title     = {Stereochemistry and complexational behaviour of dibenzo-crown ethers},
  year      = {1992},
  language  = {en}
}
@article{KleinpeterThomasUhligetal.1993,
  author    = {Kleinpeter, Erich and Thomas, Steffen and Uhlig, G. and Rudorf, Wolf-Dieter},
  title     = {Study of the distribution of pi-Electrons in Push-Pull Alkenes by 1H an 13C NMR spectroscopy},
  year      = {1993},
  language  = {en}
}
@article{LehmannKleinpeter1993,
  author    = {Lehmann, J. and Kleinpeter, Erich},
  title     = {1H NMR Lanthanideinduced Shift (LIS) investigations of highly flexible molecules : a new approach ; Part II},
  year      = {1993},
  language  = {en}
}
@article{LehmannKleinpeter1993,
  author    = {Lehmann, J. and Kleinpeter, Erich},
  title     = {1H NMR Lanthanideinduced Shift (LIS) investigations of highly flexible molecules : a new approach},
  year      = {1993},
  language  = {en}
}
@article{HaufeRolleKleinpeteretal.1993,
  author    = {Haufe, G. and Rolle, U. and Kleinpeter, Erich and Kivikoski, J. and Rissanen, K.},
  title     = {N-Heterocyclization in electrophilic haloamination reactions of 1,5-cyclooctadiene : formation of the granatanine and homotropane skeletons},
  year      = {1993},
  language  = {en}
}
@article{MaekiPihlajaKleinpeteretal.1994,
  author    = {M{\"a}ki, E. and Pihlaja, Kalevi and Kleinpeter, Erich and Hartmann, J{\"u}rgen and Schroth, W.},
  title     = {Electron impact ionization mass spectrometry of some 4,9-Dihetro-(X,X)-cyclodeca-1,6-dienes : mono- and dibenzo analogues},
  year      = {1994},
  language  = {en}
}
@article{KleinpeterHeydenreichChatterjeeetal.1994,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Chatterjee, S. K. and Rudorf, Wolf-Dieter},
  title     = {Study of the pi-electron distribution in push-pull alkenes by 1H and 13C NMR spectroscopy},
  year      = {1994},
  language  = {en}
}
@article{KleinpeterHeydenreichChatterjeeetal.1994,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Chatterjee, S. K. and Rudorf, Wolf-Dieter},
  title     = {Study of the pi-electron distribution in push-pull alkenes by 1H and 13C NMR spectroscopy, III : the conformation of 3,4-Dihydro-4-oxo-2H-thiins},
  year      = {1994},
  language  = {en}
}
@book{PihlajaKleinpeter1994,
  author    = {Pihlaja, Kalevi and Kleinpeter, Erich},
  title     = {13C NMR chemical shifts in structural and stereochemical analysis},
  series = {Methods in stereochemical analysis},
  journal   = {Methods in stereochemical analysis},
  publisher = {VCH},
  address   = {New York},
  year      = {1994},
  language  = {en}
}
@article{StarkeKochUhlemannetal.1995,
  author    = {Starke, Ines and Koch, Andreas and Uhlemann, Erhard and Kleinpeter, Erich},
  title     = {Nuclear-magnetic-resonance studies and molecular modelling of the solution structure of some dibenzo crown- ethers and their complexes},
  year      = {1995},
  language  = {en}
}
@article{StarkeKochHoldtetal.1995,
  author    = {Starke, Ines and Koch, Andreas and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich},
  title     = {1H, 13C, and 15N NMR study of the solution structure of metabridged bis(benzo-15-crown-5-ether)s},
  year      = {1995},
  language  = {en}
}
@article{OszczapowiczWawerDargatzetal.1995,
  author    = {Oszczapowicz, J. and Wawer, I. and Dargatz, M. and Kleinpeter, Erich},
  title     = {Amidines .34. N-15 NMR spectra of trisubstituted amidines - substituent effects},
  year      = {1995},
  language  = {en}
}
@article{KleinpeterKochHeydenreichetal.1995,
  author    = {Kleinpeter, Erich and Koch, Andreas and Heydenreich, Matthias and Chatterjee, S. K. and Rudorf, Wolf-Dieter},
  title     = {Study of the pi-electron distribution in push-pull alkenes by 1H and 13C NMR spectroscopy, IV : the conformation and dynamic behaviour of substituted N-Phenyl-2,3-dihydro-4(1H)-pyridones},
  year      = {1995},
  language  = {en}
}
@article{LehmannKleinpeter1995,
  author    = {Lehmann, J. and Kleinpeter, Erich},
  title     = {1H NMR lanthanide-induced shift investigations of highly flexible molecules, part III. Applications to alcohols, aldehydes, esters and amines},
  year      = {1995},
  language  = {en}
}
@article{KochStarkeKleinpeter1995,
  author    = {Koch, Andreas and Starke, Ines and Kleinpeter, Erich},
  title     = {Conformational study of Dibenzo crown ethers and their complexation with Li+ and Na+},
  year      = {1995},
  language  = {en}
}
@article{KochKleinpeter1995,
  author    = {Koch, Andreas and Kleinpeter, Erich},
  title     = {Ab-initio study and semiempirical calculations of keto-enol tautomerism of triazolopyrimidines},
  year      = {1995},
  language  = {en}
}
@article{KleinpeterStroehlPeinze1995,
  author    = {Kleinpeter, Erich and Str{\"o}hl, D. and Peinze, S.},
  title     = {Solution conformation of tripeptides by NMR spectroscopy and force field calculations},
  year      = {1995},
  language  = {en}
}
@article{KleinpeterPihlaja1995,
  author    = {Kleinpeter, Erich and Pihlaja, Kalevi},
  title     = {Functions containing a thiocarbonyl group and at least one halogen, also at least one chalcogen and no halogen},
  year      = {1995},
  language  = {en}
}
@article{Kleinpeter1995,
  author    = {Kleinpeter, Erich},
  title     = {Effect of the variation of ring size of cyclic NR2 substituents on the barrier to rotation in amides, thioamides and related compounds},
  year      = {1995},
  language  = {en}
}
@article{Kleinpeter1995,
  author    = {Kleinpeter, Erich},
  title     = {Conformational analysis of six-membered sulfur-containing heterocycles},
  year      = {1995},
  language  = {en}
}
@article{KleinpeterThomasFischer1995,
  author    = {Kleinpeter, Erich and Thomas, Steffen and Fischer, G.},
  title     = {13C and 15N NMR study of 1,2,4-Triazolo[1,5-a]pyrimidines with one tautomerism-introducing substituent},
  year      = {1995},
  language  = {en}
}
@article{KleinpeterStarkeStroehletal.1996,
  author    = {Kleinpeter, Erich and Starke, Ines and Str{\"o}hl, D. and Holdt, Hans-J{\"u}rgen},
  title     = {NMR spectroscopic study of the solution structure and complexational behaviour of bis-benzocrown ethers},
  year      = {1996},
  language  = {en}
}
@article{KleinpeterStroehlPeinzeetal.1996,
  author    = {Kleinpeter, Erich and Str{\"o}hl, D. and Peinze, S. and Brandt, W. and Schmidt, R. and Neubert, K.},
  title     = {The solution conformation of cyclic ß-casomorphine-5 analogues},
  year      = {1996},
  language  = {en}
}
@article{PihlajaLehmannSchrothetal.1996,
  author    = {Pihlaja, Kalevi and Lehmann, S. and Schroth, W. and G{\"a}ber, M. and Kleinpeter, Erich},
  title     = {Electron impact induced fragmentation of dibenzo crown ethers},
  year      = {1996},
  language  = {en}
}
@article{Kleinpeter1996,
  author    = {Kleinpeter, Erich},
  title     = {The structure of hydantoins in solution and in the solid state},
  year      = {1996},
  language  = {en}
}
@article{KleinpeterHeydenreichKalderetal.1997,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Kalder, L. and Koch, Andreas and Henning, Dietrich and Kempter, Gerhard and Benassi, Rois and Taddei, F.},
  title     = {NMR spectroscopic and theoretical structural analysis of 5,5-disubstituted hydantoins in solution},
  year      = {1997},
  language  = {en}
}
@article{GrotjahnDrexlerJaegeretal.1997,
  author    = {Grotjahn, Manuela and Drexler, Hans-Joachim and J{\"a}ger, Norbert and Kleinpeter, Erich and Holdt, Hans-J{\"u}rgen},
  title     = {Molecular dynamic and conformational study of an unsaturated 12-crown-S202 ether and its AgI complexes},
  year      = {1997},
  language  = {en}
}
@article{KochKleinpeter1997,
  author    = {Koch, Andreas and Kleinpeter, Erich},
  title     = {Study of the tautomerism by experimentally and theoretically estimated 13C and 15N chemical shifts},
  year      = {1997},
  language  = {en}
}
@article{SarodnickHilfertKempteretal.1997,
  author    = {Sarodnick, Gerhard and Hilfert, Liane and Kempter, Gerhard and Kleinpeter, Erich},
  title     = {Reactin of 2-(halogenomethyl)-quinoxalines and quinolines with hydroxybenzoic acids and their esters},
  year      = {1997},
  language  = {en}
}
@article{ThomasBruehlHeilmannetal.1997,
  author    = {Thomas, Steffen and Br{\"u}hl, Iris and Heilmann, Dieter and Kleinpeter, Erich},
  title     = {13 C NMR Chemical shift calculations for some substituted pyridines - a comparative consideration},
  year      = {1997},
  language  = {en}
}
@article{HeydenreichKochKleinpeteretal.1997,
  author    = {Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich and Zimmermann, Thomas},
  title     = {Dynamic NMR study of the flexibility of 2-amino-3-aroyl-4,6-diaryl-pyrylium salts},
  issn      = {0937-0633},
  doi       = {10.1007/s002160050205},
  year      = {1997},
  language  = {en}
}
@article{KochKleinpeter1997,
  author    = {Koch, Andreas and Kleinpeter, Erich},
  title     = {Restricted rotation about particial C, N Double Bond},
  year      = {1997},
  language  = {en}
}
@article{Kleinpeter1997,
  author    = {Kleinpeter, Erich},
  title     = {The Structure of hydantions in solution and in the solid state},
  year      = {1997},
  language  = {en}
}
@article{KleinpeterKochFischeretal.1997,
  author    = {Kleinpeter, Erich and Koch, Andreas and Fischer, G. and Askolin, C.-P.},
  title     = {13 C NMR, 15 N NMR and quantum-chemical study of the tautomerism of 2-substituted 5-ME-7-OH-1,2,4-triazolo[1,5- a]pyrimidines},
  year      = {1997},
  language  = {en}
}
@article{KleinpeterStarkeStroehletal.1997,
  author    = {Kleinpeter, Erich and Starke, Ines and Str{\"o}hl, D. and Holdt, Hans-J{\"u}rgen},
  title     = {NMR spectroscopic study of the solution structure and complexational behaviour of bis-benzocrown ethers},
  year      = {1997},
  language  = {en}
}
@article{KleinpeterHeydenreichKalderetal.1997,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Kalder, L. and Koch, Andreas and Henning, Dietrich and Kempter, Gerhard},
  title     = {NMR spectroscopic and theoretical structural analysis of 5,5-disubstituted hydantoins in solution},
  year      = {1997},
  language  = {en}
}
@article{KochThomasKleinpeter1997,
  author    = {Koch, Andreas and Thomas, Steffen and Kleinpeter, Erich},
  title     = {Ab-initio study, semi-empirical calculation and NMR spectroscopy of keto-enol tautomerism of triazolopyrimidines},
  year      = {1997},
  language  = {en}
}
@article{ReicheStarkeKleinpeteretal.1998,
  author    = {Reiche, K. B. and Starke, Ines and Kleinpeter, Erich and Holdt, Hans-J{\"u}rgen},
  title     = {Host-guest complexation of imine-type meta-bridged bis(benzo crown ether)s with alkali cations in the gas phase under FAB conditions},
  year      = {1998},
  language  = {en}
}
@article{KleinpeterHeydenreichWolleretal.1998,
  author    = {Kleinpeter, Erich and Heydenreich, Matthias and Woller, Jochen and Wolf, Gunter and Koch, Andreas and Kempter, Gerhard and Pihlaja, Kalevi},
  title     = {Configuration and stereodynamics of exo/endoisomeric push-pull alkenes of pentadiene structure},
  year      = {1998},
  language  = {en}
}
@article{HeydenreichKochRistauetal.1998,
  author    = {Heydenreich, Matthias and Koch, Andreas and Ristau, Thomas and Knoll, Susanne and Heinicke, Jochen and Sieler, Joachim and Niemitz, Matthias and M{\"u}hlst{\"a}dt, Manfred and Kleinpeter, Erich},
  title     = {Conformational analysis of sulfur-containing heterocycles ; part I: synthesis and structural determination of diastereomerically pure 4,6-bis(phenoxymethyl)-1,2,5-trithiepanes},
  year      = {1998},
  language  = {en}
}
@article{HilfertSarodnickKempteretal.1998,
  author    = {Hilfert, Liane and Sarodnick, Gerhard and Kempter, Gerhard and Kleinpeter, Erich},
  title     = {1H, 13C and 15 N NMR study and molecular modelling of 2,3- disubstituted quinoxalines with sterically hinderered aromatic and heteroaromatic substituents},
  year      = {1998},
  language  = {en}
}
@article{BenassiBregullaFriedrichetal.1998,
  author    = {Benassi, Rois and Bregulla, Antje and Friedrich, Alwin and Henning, Dietrich and Heydenreich, Matthias and Mickler, Wulfhard and Kleinpeter, Erich and Kempter, Gerhard and Schilde, Uwe and Taddei, F.},
  title     = {NMR spectroscopic and theoretical structural study of 5-exo-methylene-substituted hydantoins},
  year      = {1998},
  language  = {en}
}
@article{Kleinpeter1998,
  author    = {Kleinpeter, Erich},
  title     = {Conformational analysis of saturated six-membered oxygen-containing heterocyclic rings},
  year      = {1998},
  language  = {en}
}
@article{KleinpeterHilfertKoch1999,
  author    = {Kleinpeter, Erich and Hilfert, Liane and Koch, Andreas},
  title     = {NMR spectroscopic and ab-initio MO study of sterically hindered 2,3-disubstituted quinoxalines},
  year      = {1999},
  language  = {en}
}
@article{ReicheStarkeKleinpeteretal.1999,
  author    = {Reiche, K. B. and Starke, Ines and Kleinpeter, Erich and Holdt, Hans-J{\"u}rgen and Pihlaja, Kalevi and Oksaman, P. and Ovcharenko, V. V.},
  title     = {Fragmentation of imine-type meta-bridged bis(benzo crown ether)s under electron impact},
  year      = {1999},
  language  = {en}
}
@article{DrexlerStarkeGrojahnetal.1999,
  author    = {Drexler, Hans-Joachim and Starke, Ines and Grojahn, Manuela and Reinke, H. and Kleinpeter, Erich and Holdt, Hans-J{\"u}rgen},
  title     = {SbCl3, BiCl3 and Na+ Complexes of maleonitrile-dithiacrown ethers: synthesis, crystal structures and DEP-MS experiments},
  year      = {1999},
  language  = {en}
}
@article{GrotjahnKleinpeter1999,
  author    = {Grotjahn, Manuela and Kleinpeter, Erich},
  title     = {Conformational behaviour of N-tosyl-substituted diaza-crown ethers},
  year      = {1999},
  language  = {en}
}
@article{SchollKochHenningetal.1999,
  author    = {Scholl, S. and Koch, Andreas and Henning, Dietrich and Kempter, Gerhard and Kleinpeter, Erich},
  title     = {The influence of structure and lipophilicity of hydantoin derivatives on anticonvulsant activity},
  year      = {1999},
  language  = {en}
}
@article{GrotjahnJaegerDrexleretal.1999,
  author    = {Grotjahn, Manuela and J{\"a}ger, Norbert and Drexler, Hans-Joachim and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich},
  title     = {Molecular modeling study of the PtCl2 complexes of unsaturated S2On+1- coronands: dynamic simulations and investigation of the ring interconversion},
  year      = {1999},
  language  = {en}
}
@article{ZucchiCorniaBoeseetal.1999,
  author    = {Zucchi, Claudia and Cornia, Andrea and Boese, Roland and Kleinpeter, Erich and Alper, Howard and Palyi, Gyula},
  title     = {Preparation and molecular structures of benzyl- and phenyl-acetycobalt-carbonyls},
  year      = {1999},
  language  = {en}
}
@article{BenassiBregullaHenningetal.1999,
  author    = {Benassi, Rois and Bregulla, Antje and Henning, Dietrich and Heydenreich, Matthias and Kempter, Gerhard and Kleinpeter, Erich and Taddei, F.},
  title     = {NMR-spectroscopic and theoretical structural analysis of 5-benzyl subtituted hydantoins in solutions},
  year      = {1999},
  language  = {en}
}
@article{DrexlerGrotjahnKleinpeteretal.1999,
  author    = {Drexler, Hans-Joachim and Grotjahn, Manuela and Kleinpeter, Erich and Holdt, Hans-J{\"u}rgen},
  title     = {A novel polymeric disilver(I) complex containing both macrocyclic- and linear-coordinate silver(I) centres : [Ag-2(mn-15S(2)O(3))](infinity)(ClO4)(2 infinity) (mn-15S(2)O(3) = maleonitrile-dithia[15]crown-5)},
  year      = {1999},
  language  = {en}
}
@article{BenassiBertariniHilfertetal.2000,
  author    = {Benassi, Rois and Bertarini, C. and Hilfert, Liane and Kempter, Gerhard and Kleinpeter, Erich and Spindler, J{\"u}rgen and Taddei, F. and Thomas, Steffen},
  title     = {Exocyclic push-pull conjugated compounds : Part 3},
  year      = {2000},
  language  = {en}
}
@article{Kleinpeter2000,
  author    = {Kleinpeter, Erich},
  title     = {Recent advances in studying tautomerism in solution and in solid state},
  year      = {2000},
  language  = {en}
}
@article{StarkeHolzbergerKammetal.2000,
  author    = {Starke, Ines and Holzberger, Anja and Kamm, Birgit and Kleinpeter, Erich},
  title     = {Qualitative and quantitative analysis of carbohydrates in green juices (wild mix grass and alfalfa) from a green biorefinery by gas chromatography/mass spectrometry},
  year      = {2000},
  language  = {en}
}
@article{KleinpeterHilfertKoch2000,
  author    = {Kleinpeter, Erich and Hilfert, Liane and Koch, Andreas},
  title     = {GIAO-HF/DFT calculation of C-13 and N-15 chemical shifts for studying tautomerism and intramolecular hydrogen bonding in 2,3-disubstituted quinoxalines},
  year      = {2000},
  language  = {en}
}
@article{BenassiBertariniKleinpeteretal.2000,
  author    = {Benassi, Rois and Bertarini, C. and Kleinpeter, Erich and Taddei, F. and Thomas, Steffen},
  title     = {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},
  year      = {2000},
  language  = {en}
}
@article{BenassiBertariniKleinpeteretal.2000,
  author    = {Benassi, Rois and Bertarini, C. and Kleinpeter, Erich and Taddei, F.},
  title     = {Exocyclic push-pull conjugated compounds, Part 2 : the effect of donor and acceptor substituents on the rotational barrier of push-pull ethylenes},
  year      = {2000},
  language  = {en}
}
@article{GrotjahnLehmannAurichetal.2001,
  author    = {Grotjahn, Manuela and Lehmann, S. and Aurich, Ines and Holdt, Hans-Joachim and Kleinpeter, Erich},
  title     = {NMR spectroscopic and molecular modelling studies of the solution structure and complexational behaviour of some bis(benzocrown ether)s},
  year      = {2001},
  abstract  = {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.},
  language  = {en}
}
@article{HoldtDrexlerStarkeetal.2001,
  author    = {Holdt, Hans-J{\"u}rgen and Drexler, Hans-Joachim and Starke, Ines and Grotjahn, Manuela and Kleinpeter, Erich},
  title     = {Homologous series of the PdCl2 and PtCl2 complexes of maleonitrile-dithiacrown ethers : synthesis, crystal structures, NMR spectroscopy and mass spectrometry},
  year      = {2001},
  language  = {en}
}
@article{KleinpeterGrotjahnKlinkaetal.2001,
  author    = {Kleinpeter, Erich and Grotjahn, Manuela and Klinka, Karel D. and Drexler, Hans-Joachim and Holdt, Hans-J{\"u}rgen},
  title     = {Conformational and complexational study of some maleonitrile mixed oxadithia crown ethers by NMR spectroscopy and molecular modelling},
  year      = {2001},
  abstract  = {The macrocyclic ring interconversion of four maleonitrile mixed oxadithia crown ethers of variable ring size, mn-12-S2O2, mn-15-S2O3, mn-18-S2O4 and fn-12-S2O2, were studied by 1H and 13C NMR spectroscopy and by molecular modelling. The barriers to ring interconversion were estimated using variable temperature NMR spectroscopy and from the calculated activation energies, together with the spin-lattice relaxation times of the CH2 carbon atoms, conclusions were drawn regarding the intramolecular flexibility of the crown ethers in both the free state as well as the complexed state incorporating either AgI, BiIII, SbIII, PdII or PtII metal cations. Furthermore, both the stoichiometry of the complexes and the coordination sites of the crown ethers to the various cations were also clearly implicated. Molecular modelling was also utilised to ascertain the preferred conformers of the four compounds and their corresponding complexes, the results of which corroborated the experimental NMR results to a high degree.},
  language  = {en}
}
@article{BeitzKoetzWolfetal.2001,
  author    = {Beitz, Toralf and Koetz, Joachim and Wolf, Gunter and Kleinpeter, Erich and Friberg, Stig E.},
  title     = {Poly(N-vinyl-2-pyrrolidone) and 1-octyl-2-pyrrolidinone modified ionic microemulsions},
  year      = {2001},
  language  = {en}
}
@article{GermerKlodPeteretal.2002,
  author    = {Germer, Antje and Klod, Sabrina and Peter, Martin G. and Kleinpeter, Erich},
  title     = {NMR spectroscopic and theoretical study of the complexation of the inhibitor allosamidin in the binding pocket of the plant chitinase hevamine},
  year      = {2002},
  abstract  = {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.},
  language  = {en}
}
@article{ThieleRottmannGermeretal.2002,
  author    = {Thiele, Gabriela and Rottmann, Antje and Germer, Antje and Kleinpeter, Erich and Spindler, Klaus-Dieter and Synstad, Bjoenar and Eijsink, Vincent G. H. and Peter, Martin G.},
  title     = {Synthesis and conformational analysis of pseudosugar analogues of chitotriose},
  year      = {2002},
  abstract  = {In this article, the synthesis of analogs of N,N',N''-triacetylchitotriose in which the central sugar residue was replaced by a succinic acid is presented. Mol. modeling calcns. revealed that the pseudotrisaccharides exist in low energy extended conformations which show similar space filling as N,N',N''-triacetylchitotriose. Of the N,N',N''-triacetylchitotriose pseudosugar analogs tested as chitinase inhibitors, none showed any appreciable competition (numerical data not presented). The conformational anal. along with further synthetic efforts will hopefully lead to more efficient pseudosaccharides as chitinase inhibitors.},
  language  = {en}
}
@article{GermerPeterKleinpeter2002,
  author    = {Germer, Antje and Peter, Martin G. and Kleinpeter, Erich},
  title     = {Solution-state conformational study of the hevamine inhibitor allosamidin and six potential inhibitor analogues by NMR spectroscopy and molecular modeling},
  year      = {2002},
  abstract  = {The soln.-state conformations of the hevamine inhibitor allosamidin and six potential inhibitor analogs were studied by various NMR spectroscopic techniques and mol. modeling using force field calcns. Detn. solely of the global energy min. conformation was found to be insufficient for consensus with the NMR results, and agreement between the NMR exptl. data and the theor. calcns. was only reached by assessing the structures as population-weighted av. conformers on the basis of Boltzmann distributions derived from the calcd. relative energies. The conformations of the glycosidic linkages in the compds. were found to be similar when the sugar residues were the same, but differences were markedly evident otherwise and also for the various heterocyclic group linkages. The binding of the compds. to hevamine, which may also complex to chitinases in general, was assessed using HMQC, transfer-NOESY, and both 1-D and 2-D satn. transfer difference NMR expts. Under the conditions employed, only allosamidin was implicated to be bound to hevamine, and then only by HMQC with the dipolar coupling-based expts. failing to substantiate the formation of the complex. However, the results are consistent with the biochem. activities of the compds. whereby only allosamidin has been shown to act as a competitive inhibitor.},
  language  = {en}
}
@article{KovacsTothKleinpeteretal.2003,
  author    = {Kovacs, J. and Toth, G. and Kleinpeter, Erich and Schilde, Uwe},
  title     = {Crystal structure of trans, cis-({\~n})-3{\"i}-4-fluorophenyl)-2-phenylspiro[2H-1-benzothiopyran-34H,2{\"i}-oxiran]-4-one 1- oxide, C22H15FO3S},
  issn      = {1433-7266},
  year      = {2003},
  language  = {en}
}
@article{SarodnickHeydenreichLinkeretal.2003,
  author    = {Sarodnick, Gerhard and Heydenreich, Matthias and Linker, Torsten and Kleinpeter, Erich},
  title     = {Quinoxalines : Part 12: Synthesis and structural study of 1-(thiazol-2-yl)-1H-pyrazolo[3,4-b]quinoxalines - the dehydrogenative cyclization with hydroxylamine hydrochloride},
  year      = {2003},
  language  = {en}
}
@article{GermerMuggePeteretal.2003,
  author    = {Germer, Antje and Mugge, Clemens and Peter, Martin G. and Rottmann, Antje and Kleinpeter, Erich},
  title     = {Solution- and bound-state conformational study of N,N',N''-triacetyl chitotriose and other analogous potential inhibitors of hevamine: Application of trNOESY and STD NMR spectroscopy},
  year      = {2003},
  abstract  = {The soln.-state conformations of N,N',N''-triacetyl chitotriose (1) and other potential chitinase inhibitors 2-4 were studied using a combination of NMR spectroscopy (NOESY) and mol. mechanics calcns. Detn. solely of the global energy min. conformation was found to be insufficient for an agreement with the NMR results. An appropriate consistency between the NMR exptl. data and theor. calcns. was only reached by assessing the structures as population-weighted av. conformers based on Boltzmann distributions derived from the calcd. relative energies. Analogies, but also particular differences, between the synthetic compds. 2-4 and the naturally-occurring N,N',N''-triacetyl chitotriose were found. Furthermore, the conformation of compds. 1 and 2 when bound to hevamine was also studied using transferred NOESY expts. and the binding process was found to impart a level of conformational restriction on the ligands. The preferred conformation as detd. for 1 in the bound state to hevamine belonged to one of the conformational families found for the compd. when free in soln., although full characterization of the bound-state conformations was impeded due to severe signal overlap. Satn. transfer difference NMR expts. were also employed to analyze the binding epitopes of the bound compds. We thus detd. that it is mainly the acetyl amido groups of the trisaccharide and the heterocyclic moiety which are in close contact with hevamine.},
  language  = {en}
}
@article{TaddeiKleinpeter2004,
  author    = {Taddei, F. and Kleinpeter, Erich},
  title     = {The anomeric effect in substituted cyclohexanes : I. The role of hyperconjugative interactions and steric effect in monosubstituted cyclohexanes},
  issn      = {0166-1280},
  year      = {2004},
  abstract  = {The relative energy of conformers, DeltaE, of monosubstituted cyclohexanes with OR (R = Me, Et, i-Pr and t-Bu) and R substituents (R = Me, Et, i-Pr and t-Bu) was calculated with MO ab initio theory at RHF, MP2 and QCISD levels with the 6-311G* and 6-311 + G* basis sets. A selected group of delocalizing interactions were calculated with the natural bond orbital method in order to quantify the hyperconjugative contribution, DeltaE(hyp.), to the relative stability of conformers. From the calculated values of DeltaE and DeltaE(hyp.) an estimate of the differential steric effect, DeltaE(ster.), of substituents in cyclohexane was obtained. The values of DeltaE(hyp), and DeltaE(ster.) show that they have a similar magnitude for OR substituents, while for R substituents the values of are greater. The shift in the conformational equilibrium towards the axial conformer, the so-called anomeric effect, takes place when, within a series of substituents, hyperconjugative interactions and steric interactions balance in favour of the stability of this conformer. (C) 2004 Elsevier B.V. All rights reserved},
  language  = {en}
}
@article{SzatmariMartinekLazaretal.2004,
  author    = {Szatmari, Istvan and Martinek, T. A. and Lazar, L. and Koch, Andreas and Kleinpeter, Erich and Neuvonen, Kari and Fulop, Ferenc},
  title     = {Stereoelectronic effects in ring-chain tautomerism of 1,3-diarylnaphth[1,2-e][1,3]oxazines and 3-alkyl-1- arylnaphth[1,2-e][1,3]oxazines},
  issn      = {0022-3263},
  year      = {2004},
  abstract  = {The disubstitution effects of X and Y in 1-(Y-phenyl)-3-(X-phenyl)-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines on the ring-chain tautomerism, the delocalization of the nitrogen lone pair (anomeric effect), and the C-13 NMR chemical shifts were analyzed by using multiple linear regression analysis. Study of the three-component equilibrium B reversible arrow A reversible arrow C revealed that the chain reversible arrow trans (A reversible arrow B) equilibrium constants are significantly influenced by the inductive effect (sigma(F)) of substituent Y on the 1-phenyl ring. In contrast, no significant substituent dependence on Y was observed for the chain reversible arrow cis (A reversible arrow C) equilibrium. There was an analogous dependence for the epimerization (C reversible arrow B) constants of 1-(Y-phenyl)-3- alkyl-2,3-dihydro-1H-naphth[1,2-e] [1,3]oxazines. With these model compounds, significant overlapping energies of the nitrogen lone pair was observed by NBO analysis in the trans forms B (to sigma*(C1-C1'), sigma*(C1-C10b), and sigma*(C3-O4)) and in the cis forms C (to sigma*(C1-H), sigma*(C1-C10b), and sigma*(C3-O4)). The effects of disubstitution revealed some characteristic differences between the cis and trans isomers. However, the results do not suggest that the anomeric effect predominates in the preponderance of the trans over the cis isomer. When the C-13 chemical shift changes induced Y by substituents X and Y (SCS) were subjected to multiple linear regression analysis, negative rho(F)(Y) and rho(F)(X) values were observed at C-1 and C-3 for both the cis and trans isomers. In contrast, the positive rho(R)(Y) values at C-1 and the negative rho(R)(X) values at C-3 observed indicated the contribution of resonance structures f (rho(R) > 0) and g (rho(R) < 0), respectively. The classical double bond-no-bond resonance structures proved useful in explaining the substituent sensitivities of the donation energies and the behavior of the SCS values},
  language  = {en}
}
@article{StarkeSarodnickOvcharenkoetal.2004,
  author    = {Starke, I. and Sarodnick, Gerhard and Ovcharenko, V. V. and Pihlaja, Kalevi and Kleinpeter, Erich},
  title     = {Quinoxalines : Part 13: Synthesis and mass spectrometric study of aryloxymethylquinoxalines and benzo[b]furylquinoxalines},
  issn      = {0040-4020},
  year      = {2004},
  abstract  = {A series of new aryloxymethylquinoxalines, benzo[b]- and naphtho[2,1-b] fury] quinoxalines, possessing potential biological activity, was prepared, characterized by IR and NMR spectroscopy and their electron ionization (EI) mass spectra studied in detail. The aryloxymethylquinoxalines were obtained by reacting halogenomethylquinoxalines with bifunctional O-nucleophiles. The benzo[b]furylquinoxalines and naphtho[2, I -b]furylquinoxalines were prepared via two routes, which differed in the order of the two cyclization steps involved in the syntheses. The composition of the ions obtained by El mass spectrometry were determined by accurate mass measurements and the fragmentation pathways clarified by B/E linked scans and collision induced dissociation. The mass spectrometric behaviour of the compounds studied as to the possible loss of OH' radicals proved to be very characteristic. (C) 2004 Elsevier Ltd. All rights reserved},
  language  = {en}
}
@article{HausmannKassKlodetal.2004,
  author    = {Hausmann, J. and Kass, S. and Klod, Sabrina and Kleinpeter, Erich and Kersting, Berthold},
  title     = {Binucleating aza-sulfonate and aza-sulfinate macrocycles : Synthesis and coordination chemistry},
  issn      = {1434-1948},
  year      = {2004},
  abstract  = {The preparation and ligating properties of S-oxygenated derivatives of a macrobinucleating hexaazadithiophenolate macrocycle H2L1 of the Robson type towards nickel(II) and zinc(II) ions are reported. Nickel complexes of the hexaazadiphenylsulfonate ligand (L-2)(2-)[(L-2)Ni-2(II)(mu-L)](+)(L = m-Cl-OBz(-) (3), Cl- (4) and OAc- (6)] are readily obtained in high yields by oxidation of the respective [(L-1)Ni-2(II)(mu-L)](+) parent complexes [L = m- Cl-OBz- (2), Cl- (1), OAc- (5)] with meta-chloroperoxybenzoic acid or hydrogen peroxide. Decomposition of the sulfonate complexes gives the free macrocycle H2L2 which, upon treatment with Zn(OAc)(2)(.)2H(2)O, produces the diamagnetic zinc complex [(L-2)Z(2)(II)(OAc)](+) (8). A dinuclear Cu-II complex of the hexaazadisulfinate derivative (L-3')(2-), [(L-3)CU2II](2+) (9), is formed rather unexpectedly by air oxidation of (L-1)(2-) in the presence of Cu-I. The crystal- structure determinations of the perchlorate or tetraphenylborate salts of 2, 3, and 4 show that the new ligands support the formation of binuclear complexes with bowl-shaped, calixarene-like binding cavities. NMR spectroscopic studies of 8 show that the complexes retain their solid-state structures in solution. A crystal-structure determination of 9 reveals two five-coordinate Cu-II ions bridged by the two sulfinate functions of (L-3)(2-)},
  language  = {en}
}
@article{MiklosKanizsaiThomasetal.2004,
  author    = {Miklos, F. and Kanizsai, I. and Thomas, Steffen and Kleinpeter, Erich and Sillanpaa, R. and Stajer, G.},
  title     = {Preparation and structure of diexo-oxanorbornane-fused 1,3-heterocycles},
  issn      = {0385-5414},
  year      = {2004},
  abstract  = {Via the reaction of diexo-oxanorbornanedicarboxylic anhydride with toluene, the diexo-aroylcarboxylic acid (3a) was prepared, which exists partly as the tautomeric lactol (3b). With bifunctional reagents, 3a yields fused heterocycles containing three-six rings. Thus, alkylenediamines result in imidazole- and 1,3-diazepine-fused oxygen- bridged isoindolones (6a,b), alkanolamines form the oxazole- and 1,3-oxazine-fused oxanorbornene derivatives (7a-c), and o-phenylenediamine undergoes cyclization to furnish the condensed benzimidazole (8). The reaction of 3a with diexo- aminonorbornanecarbohydrazide yields a pyrimidopyridazine containing six condensed rings (9). In a similar reaction with diendo-aminonorbornenecarbohydrazide, cyclopentadiene cleaves off to give the tricyclic retro Diels-Alder product (10). The structures, and particulary the configurations at the oxanorbornane ring systems and the position of the aryl substituent, were established by means of 1D- and 2D-NMR spectroscopy and, for 3b and 7c, also by X-Ray measurements},
  language  = {en}
}
@article{KochMikhovaKleinpeter2004,
  author    = {Koch, Andreas and Mikhova, Bozhana and Kleinpeter, Erich},
  title     = {Ab initio MP2/GIAO/NBO study of the delta-syn-axial effect in C-13 NMR spectroscopy},
  issn      = {0022-2860},
  year      = {2004},
  abstract  = {The C-13 chemical shifts of 20 rigid bicyclic compounds have been calculated with ab initio HF and MP2 methods. The calculations showed very good reproducibility of the experimental values. The molecular orbital interactions in the rigid, nearly planar delta-syn-axial fragments in the isomeric groups of norbornane derivatives 1.x-4.x were studied in detail and were employed to explain the deshielding delta-syn-axial effect in C-13 NMR spectroscopy. (C) 2004 Elsevier B.V. All rights reserved},
  language  = {en}
}
@article{KleinpeterSeidl2004,
  author    = {Kleinpeter, Erich and Seidl, Peter Rudolf},
  title     = {The gamma- and the delta-effects in C-13 NMR spectroscopy in terms of nuclear chemical shielding (NCS) analysis},
  year      = {2004},
  abstract  = {Carbon-13 NMR is widely used in the determination of the stereochemistry of organic compounds. Changes in chemical shifts caused by interactions of groups that are close in space normally result in shielding of the carbon and deshielding of the hydrogen nuclei that are involved. This is not always the case, however, and further work on the origin of these effects would be desirable. Early applications of theoretical methods to the study of NMR shielding parameters were not particularly successful, but in recent years, the calculation of NMR shielding parameters by theoretical methods has developed into a useful and popular tool for structural studies by NMR. A promising approach to the problem of distinguishing and evaluating stereochemical influences on carbon and hydrogen chemical shifts is provided by natural chemical shielding (NCS) analysis. This method allows a partitioning of theoretical NMR shieldings into magnetic contributions from bonds and lone pairs of the molecule using the natural bond orbital (NBO) method. In order to investigate the origins of steric effects, we employed the NCS analysis to axial/equatorial-Me-cyclohexane, norbornane and exo/endo-Me-norbornane, in addition to n-pentane in the anti, gauche and g(P) g(M) conformations. Our results indicate that distortions in molecular structure due to steric effects can result in bond stretching or compression or in angular distortions. Changes in bond lengths result in the predictable shielding or deshielding of the nuclei that are involved. Where the molecular framework may be distorted to alleviate strain, chemical shifts appear to reflect changes in angles. Copyright (C) 2004 John Wiley Sons, Ltd},
  language  = {en}
}
@article{KleinpeterKlodRudorf2004,
  author    = {Kleinpeter, Erich and Klod, Sabrina and Rudorf, Wolf-Dieter},
  title     = {Electronic state of push-pull alkenes : an experimental dynamic NMR and theoretical ab initio MO study},
  year      = {2004},
  abstract  = {The H-1 and C-13 NMR spectra of a number of push-pull alkenes were recorded and the C-13 chemical shifts calculated employing the GIAO perturbation method. Of the various levels of theory tried, MP2 calculations with a triple- zeta-valence basis set were found to be the most effective for providing reliable results. The effect of the solvent was also considered but only by single-point calculations. Generally, the agreement between the experimental and theoretically calculated C-13 chemical shifts was good with only the carbons of the carbonyl, thiocarbonyl, and cyano groups deviating significantly. The substituents on the different sides of the central C=C partial double bond were classified qualitatively with respect to their donor (S,S < S,N < N,N) and acceptor properties (CdropN < C=O < C=S) and according to the ring size on the donor side (6 < 7 < 5). The geometries of both the ground (GS) and transition states (TS) of the restricted rotation about the central C=C partial double bond were also calculated at the HF and MP2 levels of theory and the free energy differences compared with the barriers to rotation determined experimentally by dynamic NMR spectroscopy. Structural differences between the various push-pull alkenes were reproduced well, but the barriers to rotation were generally overestimated theoretically. Nevertheless, by correlating the barriers to rotation and the length of the central C=C partial double bonds, the push-pull alkenes could be classified with respect to the amount of hydrogen bonding present, the extent of donor-acceptor interactions (the push-pull effect), and the level of steric hindrance within the molecules. Finally, by means of NBO analysis of a set of model push-pull alkenes (acceptors: - CdropN, -CH=O, and -CH=S; donors: S, O, and NH), the occupation numbers of the bonding pi orbitals of the central C=C partial double bond were shown to quantitatively describe the acceptor powers of the substituents and the corresponding occupation numbers of the antibonding pi* orbital the donor powers of the substituents. Thus, for the first time an estimation of both the acceptor and the donor properties of the substituents attached to the push-pull double bond have been separately quantified. Furthermore, both the balance between strong donor/weak acceptor substituents (and vice versa) and the additional influences on the barriers to rotation (hydrogen bonding and steric hindrance in the GSs and TSs) could be differentiated},
  language  = {en}
}
@article{KleinpeterKlod2004,
  author    = {Kleinpeter, Erich and Klod, Sabrina},
  title     = {Ab initio calculation of the anisotropic/ring current effects of amino acid residues to locate the position of substrates in the binding site of enzymes},
  year      = {2004},
  abstract  = {The ring current effects of aromatic moieties and the anisotropic effects of the C=O and C-X (X = C, N, S) bonds and of the NH=C(NH2)-NH- moiety in the side chains of amino acid residues of proteins were ab initio calculated based on nuclear independent chemical shieldings as employed by P.v.R. Schleyer. Hereby, quantitative information about the spatial extension, sign and scope of the corresponding ring current/anisotropic effects was obtained and they were visualized as iso-chemical-shielding-surfaces. Examining this quantitative information compared with experimental NMR chemical shifts, the role of the corresponding amino acid residues in binding substrates in the binding site of enzymes was studied. (C) 2004 Elsevier B.V. All rights reserved},
  language  = {en}
}
@article{HolzbergerKleinpeter2004,
  author    = {Holzberger, Anja and Kleinpeter, Erich},
  title     = {Solution structure of the palladium(II) complex of 1,4,7,10-tetrathiacyclododec-2-ene-2,3-dicarbonitrile},
  issn      = {0749-1581},
  year      = {2004},
  abstract  = {The solution structure of the Pd(II) complex of mn-12-S-4 was studied in detail by NMR spectroscopy. The stoichiometry of the complex was determined by H-1 NMR titration experiments. (3)J(H,H) coupling constants were extracted from the 2D J-resolved NMR spectrum of the complex providing information concerning the S-C-C-S torsional angles. Further conclusions about the conformation of [Pd(mn-12-S-4)](BF4)(2) were drawn from experimental NOES. The results of the NMR study were corroborated by molecular modelling. Copyright (C) 2004 John Wiley Sons, Ltd},
  language  = {en}
}
@article{HolzbergerHoldtKleinpeter2004,
  author    = {Holzberger, Anja and Holdt, H. N. and Kleinpeter, Erich},
  title     = {NMR spectroscopic and molecular modelling study of the solution structure and the complexational behavior of maleonitrile tetrathia crown ethers with silver(I)},
  year      = {2004},
  abstract  = {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},
  language  = {en}
}
@article{HolzbergerHoldtKleinpeter2004,
  author    = {Holzberger, Anja and Holdt, Hans-J{\"u}rgen and Kleinpeter, Erich},
  title     = {Conformational analysis of mixed oxathia crown ethers and their complexational ability towards Ag(I) and Pd(II) : an experimental solution NMR and theoretical molecular modelling study},
  issn      = {1477-0520},
  year      = {2004},
  abstract  = {Both the conformation and flexibility of four mixed oxathia crown ethers and their Ag(I) and Pd(II) complexes were studied by H-1 NMR (delta, J, NOE, T-1), C-13 NMR, dynamic 1H NMR spectroscopy and molecular modelling. The stoichiometry and stability constants of the complexes were determined from corresponding Job's plots in the case of Ag(I) complexes as the interchange between free and complexed states was fast on the NMR timescale; interchange for the Pd(II) complexes was sufficiently slow such that distinct sub-spectra were observable for the free and complexed states. In all cases where complexation was observed, 1 : 1 complexes were formed. Global minima structures determined from the modelling studies were analysed with respect to the barriers to ring interconversion, the flexibility of the species in solution and the preferred complexation of Ag(I) and Pd(II) to the sulfur atoms of the crown ethers},
  language  = {en}
}
@article{KleinpeterKlod2004,
  author    = {Kleinpeter, Erich and Klod, Sabrina},
  title     = {Separation of anisotropic and steric substituent effects - nuclear chemical shielding analysis of H-4 and C-4 in phenanthrene and 11-ethynylphenanthrene},
  year      = {2004},
  abstract  = {The anisotropic effect of a proximally introduced ethynyl group on the chemical shifts of H-4 and C-4 of the phenanthrene skeleton was calculated using GIAO-HF/NICS methodology. The anisotropic effect, long considered to be the source of the considerable downfield shift of H-4 in 11-ethynylphenanthrene in comparison to the chemical shift value of the corresponding proton in phenanthrene, was determined to be only negligible in magnitude on the basis of these calculations. Partitioning of the natural chemical shieldings of H-4 and C-4 by the NCS-NBO method into various contributions from the C-C and C-H bonds present in each molecule revealed that steric compression was able to account for the large downfield shifts of both H-4 and C-4 in 11-ethynylphenanthrene relative to phenanthrene. Thus, the substituent effect is almost totally permeated by this latter interaction and not by the aforementioned process, which was previously presumed to be the sole underlying cause},
  language  = {en}
}
@article{HeydenreichKochKovacsetal.2004,
  author    = {Heydenreich, Matthias and Koch, Andreas and Kovacs, J. and Toth, G. and Kleinpeter, Erich},
  title     = {Electronic influences on (3)J(C,H) coupling constants via -S-, -S(O)- and -SO2--: their determination, calculation and comparison of detection methods},
  issn      = {0749-1581},
  year      = {2004},
  abstract  = {(3)J(C,H) coupling constants via a sulfur atom in two series of compounds, both including a sulfide, a sulfoxide and a sulfone, were detected experimentally and calculated by quantum mechanical methods. In the first series (1-3) the coupling between a hydrogen, bonded to an Sp(3) carbon, and an Sp(2) carbon is treated; the second series (4- 6) deals with the coupling between a hydrogen, bonded to an Sp3 carbon, and an Sp3 carbon. Different pulse sequences (broadband HMBC, SelJres, 1D HSQMBC, J-HMBC-2, selective J-resolved long-range experiment and IMPEACH-MBC) proved to be useful in determining the long-range (3)J(C,H) coupling constants. However, the dynamic behaviour of two of the compounds (4 and 6) led to weighted averages of the two coupling constants expected (concerning equatorial and axial positions of the corresponding hydrogens). DFT calculations proved to be useful to calculate not only the (3)J(C,H) coupling constants but also the different contributions of FC, PSO, DSO and SD terms; the calculation of the Fermi contact term (FC) was found to be sufficient for the correct estimation of (3)J(C,H) coupling constants. Copyright (C) 2004 John Wiley Sons, Ltd},
  language  = {en}
}
@article{HeydenreichWolfWolleretal.2004,
  author    = {Heydenreich, Matthias and Wolf, G. and Woller, Jochen and Kleinpeter, Erich},
  title     = {Restricted rotation of the amino group and ring inversion in highly substituted anilines. A dynamic NMR and computational study},
  issn      = {0040-4020},
  year      = {2004},
  abstract  = {The reaction of cyclic ylidene malononitriles with acetylene (di)carboxylic acid esters led to the production of nine bicyclic systems incorporating highly substituted (5/6) anilines. The free energy of activation (DeltaG(\#)) for the restricted rotation about the aniline-NH2 bond was experimentally measured in each case and a correlation was evident between the increase in steric strain in the ground state, the electron withdrawing capabilities of the ring substituents, and a reduction in the rotational barrier. For four of the compounds, the slow ring interconversion (chairreversible arrowchair) for the annelated saturated seven-membered ring that formed part of the bicyclic system was also evident. In these four compounds, both dynamic processes were also studied theoretically using ab initio methods whilst the ring interconversion was additionally studied using molecular dynamic simulations. The interconversion between the two stable chair forms was deemed to occur via a conformation series consisting of chairreversible arrowboatreversible arrowtwist-boatreversible arrowboatreversible arrowchair. (C) 2004 Elsevier Ltd. All rights reserved},
  language  = {en}
}
@article{KoetzGuentherKosmellaetal.2004,
  author    = {Koetz, Joachim and G{\"u}nther, Claudia and Kosmella, Sabine and Kleinpeter, Erich and Wolf, Gunter},
  title     = {Polyelectrolyte induced structural changes in the isotropic phase of the system sulfobetaine/pentanol/toluene/ water},
  year      = {2004},
  language  = {en}
}
@article{VirtaKochRoslundetal.2005,
  author    = {Virta, P. and Koch, Andreas and Roslund, M. U. and Mattjus, P. and Kleinpeter, Erich and Kronberg, L. and Sjoholm, R. and Klika, Karel D.},
  title     = {Synthesis, characterisation and theoretical calculations of 2,6-diaminopurine etheno derivatives},
  issn      = {1477-0520},
  year      = {2005},
  abstract  = {Four derivatives of 2,6-diaminopurine (1) were synthesised and characterised. When 1 was reacted with chloroacetaldehyde, 5-aminoimidazo[2,1- i] purine (2), 9-aminoimidazo[2,1-b]purine (3), 9-aminoimidazo[1,2- a]purine (4) and diimidazo[2,1-b: 2', 1'-i]purine (5) were formed. The purified products (3 - 5) were fully characterised by MS, complete NMR assignments as well as fluorescence and UV spectroscopy. The purified, isolated yields of these products ( 3 - 5) varied from 2.5 to 30\%. The relative stability of different tautomers was investigated by theoretical calculations. Fluorescence characteristics are also discussed and compared to the starting material 1 and a reference molecule 2-aminopurine},
  language  = {en}
}
@article{WolfKleinpeter2005,
  author    = {Wolf, G. and Kleinpeter, Erich},
  title     = {Pulsed field gradient NMR study of anomalous diffusion in a lecithin-based microemulsion},
  issn      = {0743-7463},
  year      = {2005},
  abstract  = {Self-diffusion measurements in microemulsion systems composed of a naturally occurring soybean lecithin mixture, an aqueous phase, either water or a 1\% aqueous PDADMAC solution, and isooctane were accomplished by pulsed field gradient (PFG) (HNMR)-H-1 spectroscopy at oil dilution lines of low and intermediate water/lecithin ratios. The concentration-dependent diffusion data reveal water-in-oil (W/O) reverse micellar aggregates with dimensions on the nanometer scale being slightly smaller at low water content. With increasing micellar volume fractions, both hydrodynamic as well as direct interactions between particles significantly slow aggregate diffusion. The surfactant mean square displacements (msd's) in dilute and concentrated polymer-free systems studied as a function of diffusion time (20-1000 ms) are characterized by a crossover from Gaussian diffusion, due to slow aggregate motion, to anomalously enhanced diffusion, due to fast surface-bulk surfactant exchange at intermediate times revealing weak, barrier-controlled adsorption behavior. Upon addition of the polycation PDADMAC, the diffusion characteristics change to exclusively superdiffusive behavior with surfactant msd scaling with time as t(3/2) over the entire time range studied. This is caused by surfactant molecules performing Levy walks along the surface of reverse micelles mediated by the dilute bulk. The bulk-mediated surface diffusion is a consequence of the diffusion-controlled micelle-bulk exchange dynamics induced by interactions of PDADMAC with surfactant headgroups},
  language  = {en}
}