Quantenmechanische Berechnung der CD-Spektren von Cyclohexandionderivaten, Lactamen, Ribonuclease A sowie von Androstan-Bisporphyrinen

Subject of this thesis is the calculation of Circular Dichroism (CD)-spectra of different compounds. The prediction of the long wavelength part of the spectra is of special interest. Semiempirical and ab initio calculations were performed on cyclohexandione derivatives, bicyclic lactams, the protein Ribonuclease A and androstan-bisporphyrins. The objective for the smaller molecules was to predict the absolute configuration of the compounds by comparing the calculated and experimental CD-spectra. The CD-spectrum of the cyclohexandione derivatives could qualitatively be reproduced with the semiempirical method CNDO/2S and with an ab initio method. The empirical octant-rule could also be successfully applied to these compounds and the predictions of the octant rule have been verified by the quantum chemical calculations. Calculations on bicyclic lactams have been performed with ab initio methods, which reproduced the experimental X-ray diffraction geometries and the experimental CD-spectra well. In the bicyclic lactams under consideration the planarity of the peptide group is disturbed by the rigid bicyclic skeleton. Calculations on these lactams with enforced planarity of the peptide group showed, that neglect of the nonplanarity can lead to wrong predictions of the CD. The CD of the protein Ribonuclease A has been calculated with the so-called Matrix-Method, based geometries obtained by molecular dynamics calculations. Here, it should be tested, if the calculated CD-spectrum can be improved in comparison to former calculations on the basis of the X-ray diffraction geometry of Ribonuclease A. The CD-spectrum calculated in this way was less consistent with the experimental spectrum than the one calculated on the basis of the X-ray diffraction geometry. Analysis of the x-ray diffraction geometries showed that the peptide groups in the protein are not planar. The program MATMAC, which has been developed in our group, assumes the peptide groups to be planar, so that taking the nonplanarity of the peptide groups into account could probably improve the results of the program. The relevant geometries of the bisporphyrins have been calculated with a Monte Carlo method combined with a force field (MMFF94). The CD calculations with the program MATMAC and the dipole-dipole method on the basis of these geometries could qualitativly reproduce the experimental CD-spectra.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2001

Author dc:creator

• Gabriel, Sven

Contributors dc:contributor

• Fleischhauer, Jörg

• info:eu-repo/classification/ddc/540
• Chemie
• Cyclohexandione
• Lactame
• Bicyclische Verbindungen
• Ribonuclease A
• Porphyrine
• Androstanderivate
• Zirkulardichroismus
• Ab-initio-Rechnung

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-118943%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A56863