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Title graphics: Two independent statistical models for evaluating the certainties of configurational assignments of compounds based on nuclear magnetic resonance (NMR) data are evaluated and compared. Both methods yield weights or probabilities with which two or more structure models (constitutional or configurational isomers or even conformers) could be differentiated based on experimental parameters. Although this paper focusses on the use of residual dipolar couplings (RDCs) for the differentiation of diastereomers, the concept can be expanded to any set of experimental NMRderived parameters. It is demonstrated that highly reliable configurational assignments crucially must depend on thorough statistical analysis, which is frequently neglected in the literature.
For further details see: Configurational Analysis by Residual Dipolar Couplings: A Critical Assessment of Diastereomeric Differentiabilities.
S. Immel, M. Köck, and M. Reggelin, Chirality 2019, 384-400; DOI: 10.1002/chir.23065.
See also: ConArch+: Configurational and Conformational Architect
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Title graphics: A new method implemented into a computer program (ConArch+) has been developed and applied to demonstrate the successful implementation of residual dipolar couplings (RDCs) in distance geometry (DG) calculations for the configurational assignment of chiral compounds. Unlike established protocols, the new approach combines floating chirality (fc) in 4D and 3Ddistance bounds driven dynamics (DDD) calculations with structural information from RDCs. Thus, relative configurations of chiral compounds were generated only by observables (e.g. NOEs, RDCs) rendering tedious evaluations of calculated structures against RDCs obsolete. We demonstrate the potential of this novel procedure by the simultaneous determination of the configuration and the conformation of three natural products, (-)-isopinocampheol (1), tubocurarine (2), and vincristine (3), as well as for diisopropylidene-β-D-fructopyranose (4).
For further details see: Configurational Analysis by Residual Dipolar Coupling Driven Floating Chirality Distance Geometry Calculations.
S. Immel, M. Köck, and M. Reggelin, Chem. Eur. J. 2018, 13918-13930; DOI: 10.1002/chem.201802800.
See also: ConArch+: Configurational and Conformational Architect
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Title graphics: Reactive quinodimethane intermediates play a crucial role during the Gilch polymerization, leading to poly(para-phenylene-vinylene) (PPV) polymers.
As electrically conducting polymers, which also show electroluminescence properties, PPV are major components in organic light emitting devices (OLEDs) of the next generation.
The graphics show the singlet ground state (left: HOMO and center: LUMO) as well as excited triplet state (right: spin density contours) of α-bromo-2,5-dimethoxy-quniodimethane.
Extensive studies and DFT calculations will shed a light on the role of these intermediates during the polymerizations proceses.
For further details see: Toward Controlled Gilch Synthesis of Poly(p-phenylene vinylenes): Anionic vs Radical Chain Propagation, a Mechanistic Reinvestigation.
T. Schwalm, J. Wiesecke, S. Immel, and M. Rehahn, Macromolecules 2007, 40, 8842-8854.
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Title graphics: The double-bridged hemicarcerand was synthesized, which features nitrogen and oxygen donor atoms located on the interior of the spherical cavity and thus allows endohedral coordination of metal ions.
The Cu-II complex was studied in detail by electron paramagnetic resonance (EPR) spectroscopy and density functial theory (DFT) calculations,
with excellent agreement of proton-copper distances derived from both methods.
For further details see: Electron Paramagnetic Resonance Structure Investigation of Copper Complexation in a Hemicarcerand.
A. Gembus, B. Corzilius, R.-A. Eichel, K.-P. Dinse, S. Immel, D. Stumm, M. Flauaus, and H. Plenio, J. Phys. Chem. B 2006, 110, 15012-15020.
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Title graphics: Calculated structure of the β-cyclodextrin derived heptakis(2,3-dideoxy-2,3-epithio)-β-cycloallin (left: ball-and-stick model; center: CPK-type model; right: transparent surface model),
indicating the seven sulfur atoms pointing inside of the central cavity and towards the symmetry axis of the molecule.
For further details see: The First Synthesis of a Cycloallin Derivative from β-Cyclodextrin: Heptakis(2,3-dideoxy-2,3-epithio)-β-cycloallin.
M. Fukudome, T. Shiratani, Y. Nogami, D.-Q. Yuan, K. Fujita, and S. Immel, Angew. Chem. 2005, 117, 4273-4276; Angew. Chem. Int. Ed. Engl. 2005,44, 4201-4204.
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