Kernresonanzspektroskopische Konformationsanalyse an Cyclohexanderivaten

Feltkamp, Herbert; Franklin, Norman C.

doi:10.1002/ange.19650771709

Cited by 53 publications

(4 citation statements)

References 103 publications

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“…The diastereotopic assignment of the 2 H-C(36) was not accomplished in this work because no unambiguous differentiation could be done with the few available NOES including this group. To illustrate the assignment, a detailed description of the assignment procedure is given for the molecular fragment C(17) to C (26). First a cross-section through the z-filtered TOCSY spectrum at F, =2.20 ppm (H-C(23)) shows all coupled protons from H-C(18) to H-C (25), including CH3(45) and CH3(46) (Fig.…”

Section: *)mentioning

confidence: 99%

“…Even at 600 MHz, it is almost impossible to completely resolve a few very crowded m's of the six-membered-ring protons. In these cases, the frequency difference between the two limiting lines of them, which represents the sum of all homonuclear coupling constants to the neighbour protons are used to differentiate between the axial or equatorial position of the corresponding proton [26].…”

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confidence: 99%

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Structure of Rapamycin: An NMR and Molecular‐Dynamics Investigation

Kessler

Haeßner

Schuler

1993

Helvetica Chimica Acta

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(1 9.x. 92) ~~The highly active immunosuppressive antibiotic rapamycin is a specific inhibitor of a signal transduction pathway that results in exocytosis and transcription. We report the results of the homo-and heteronuclear NMR experiments of rapamycin in DMSO leading to a complete assignment of the 'H-and I3C-NMR signals. With exception of one CH, group, all diastereotopic assignments could be achieved using heteronuclear long-range coupling constants. Restrained molecular-dynamics simulation in the same solvent as the NMR experiments led to a well defined conformation of the rapamycin molecule in solution. Differences between the solution and crystal structures are discussed.

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confidence: 99%

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confidence: 99%

Structure of Rapamycin: An NMR and Molecular‐Dynamics Investigation

Kessler

Haeßner

Schuler

1993

Helvetica Chimica Acta

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“…Sterisch anspruchsvolle Ringsubstituenten nehmen in den Sesselkonformationen mit wenigen Ausnahmen bevorzugt die ~iquatoriale Position ein (man vergleiche z.B. : Hirsch, 1967;Eliel, 1965Eliel, , 1972Feltkamp & Franklin, 1965;Romers, Altona, Buys & Havinga 1969). Der Unterschied in der freien Standardbildungsenthalpie zwischen Sessel-und Twistformen betr~igt bei Cyclohexanen im Mittel etwa 5,5 kcal/mol.…”

Section: Molekiilgestaltunclassified

Kristall- und Molekülstruktur von cis-Dithiodihydrazido-dimetaphosphorsäure-diphenylester

Engelhardt¹,

Hartl²

1976

Acta Crystallogr Sect B

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Crystals of the title compound, C6Hs-O-(S)P(NH-NH)zP(S)-O-C6Hs, are monoclinic, a= 18"559 (7), b= 7.334 (2), c= 13-073 (5) A, ,8= 113.24 (3) °, space group C2/e, Z=4. The crystal structure was determined from X-ray diffraction data collected on a four-circle diffractometer by means of Patterson and difference Fourier syntheses and was refined by the method of least squares to an R value of 0.037 for 1345 reflexions. The molecules possess point symmetry 2. The phosphorus-hydrazine heterocycle has a twist conformation with P-N-N angles of 120.3 and 116-5 °, almost equal to those found in the chair conformation of the trans isomer. The N-P-N angle of 101"4 ° is smaller than in the chair form. The two P-N bonds (1-645 and 1.662 ~) are shorter than expected for single bonds. The N-N bond length is 1.400/~,. The two structures of the title compound and its isomer are the first example of twist and chair conformations being confirmed by X-ray analysis for a pair of cis-trans isomers of a sixmembered 1,4-substituted saturated ring system.

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“…Table 1 gives the compounds studied together with the line widths in 1/6 signal height of the tertiary cyclohexane proton to the OOCR side. This n.m.r.-parameter, A Y~/~, has been used [5] (2) One CH, group separating c.g. CN or COOEt from the ring is sufficient to exclude the a,aconformer from the conformational equilibrium within the experimental uncertainty.…”

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confidence: 99%